Method and apparatus for generating modulation signals

ABSTRACT

A method of generating modulation signals is disclosed including generally three steps. A plurality of modulation signals are generated, each of which is to be transmitted from a different one of a plurality of antennas in an identical frequency band, wherein each modulation signal includes a pilot symbol sequence including a plurality of pilot symbols used for demodulation. Each of the pilot symbol sequences is inserted at the same temporal point in each modulation signal, wherein the pilot symbol sequences are orthogonal to each other with zero mutual correlation among the plurality of modulation signals, each pilot symbol having a non-zero amplitude, the quantity of the plurality of pilot symbols in each sequence being greater than the quantity of the plurality of modulation signals to be transmitted. The plurality of modulation signals each including different transmission data and one of the pilot symbol sequences are output to the antennas.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/409,034 filed Feb. 29, 2012, which is a continuation of U.S.application Ser. No. 12/698,917 filed Feb. 2, 2010, which is acontinuation of U.S. application Ser. No. 10/486,895 filed Feb. 17,2004, which is the National Stage of International Application No.PCT/JP2002/11827, filed Nov. 13, 2002, which claims priority fromJapanese Application No. 2002-325194, filed Nov. 8, 2002; JapaneseApplication No. 2002-069716, filed Mar. 14, 2002; Japanese ApplicationNo. 2002-000359, filed Jan. 7, 2002; and Japanese Application No.2001-347029, filed Nov. 13, 2001, the disclosures of which areincorporated herein in their entirety.

TECHNICAL FIELD

The present invention relates to a transmission method for multiplexingmodulation signals of a plurality of channels to the same frequencyband, a transmission apparatus and a reception apparatus.

BACKGROUND ART

This kind of transmission method and reception method have beenavailable such as the ones disclosed in Japanese Patent ApplicationNon-Examined Publication No. 2002-44051. FIG. 87 illustrates thetransmission method and the reception method disclosed in the foregoingpublication.

In FIG. 87, first space-time encoder STE1 (8705) receives first datablock b1 [n, k], and second space-time encoder STE2 (8707) receivessecond data block b2 [n, k], and two signals coded by encoders STE1 andSTE2 respectively are modulated by inverse fast Fourier transformersIFFT (8708-8711). Then the modulated signals are transmitted as OFDM(orthogonal frequency division multiplexing) signals by fourtransmitting antennas TA1 (8712)-TA4 (8715).

A plurality of receiving antennas RA1 (8701)-RAP (8703) receive thosesignals transmitted by antennas TA1 (8712)-TA4 (8715). Reception signalsr1 [n, k] (8716)-rp (8718) are transformed by fast Fouriertransformation (FET) sub-systems FFT1 (8719)-FFTp (8721) respectively,and supplied to space-time processor STP (8722). Processor STP (8722)detects signal information and supplies it to first and secondspace-time decoders STD1 (8723) and STD2 (8724). Channel parameterestimation unit CPE (8725) receives the transformed signal, anddetermines channel-parameter information, then supplies the informationto the space-time processor STP (8722) for demodulating the signals.

However, the foregoing conventional structure gives no thought to thesynchronization between channels in the same frequency band as well as afrequency offset. As a result, this structure encounters the difficultyof achieving the most important factor in order to demultiplex amultiplexed signal, namely, obtaining an accuracy of estimatingchannels.

DISCLOSURE OF THE INVENTION

The present invention aims to provide a transmission method forestimating channels accurately and with ease from multiplexed modulationsignals. The present invention also aims to provide a transmissionapparatus and a reception apparatus, both of which can use the foregoingtransmission method.

In a transmission method for multiplexing modulation signals of aplurality of channels to the same frequency band, the present inventionachieves the following advantage: When a symbol used for demodulation isinserted in a channel, in another channel symbol, both of the same phasesignal and a quadrature signal in the in-phase-quadrature plane are madeto be zero signals. Thus, the received multiplexed modulation signalscan be demultiplexed with ease.

The transmission method of the present invention transmits modulationsignals of a plurality of channels available in the same frequency bandfrom a plurality of antennas. A symbol used for demodulation is insertedin a given channel at a certain time, while in another channel symbol atthe time, the same phase and quadrature signals in thein-phase-quadrature plane are made to be zero signals.

With this method, multiplexing the modulation signals of a plurality ofchannels to the same frequency allows increasing a data transmissionrate, and also allows estimating channels with ease. Because the symbolused for demodulation has not undergone the time multiplexing, so thatthe demodulation symbol can be isolated with ease at the receptionapparatus.

The transmission method of the present invention inserts successively aplurality of the symbols used for demodulation into a frame. Thus, thesymbols can withstand noises, so that an accuracy of channel estimationat the reception apparatus is increased. As a result, the quality ofdata transmission can be improved.

The transmission method of the present invention places the symbols usedfor demodulation at an identical time of the respective channels andorthogonally to each other. This preparation, i.e., the symbols used fordemodulation are placed to be orthogonal to each other, allows thereception apparatus to isolate the symbols with ease for estimatingchannels.

The transmission method of the present invention transmits modulationsignals of a plurality of channels available in the same frequency bandfrom a plurality of antennas, and inserts the symbol used fordemodulation into a given channel in the OFDM frame structure. Insymbols of other channels of sub-carrier at the time when the symbol isinserted, both of the same phase signal and a quadrature signal in thein-phase-quadrature plane are made to be zero signals. With this method,multiplexing the modulation signals of a plurality of channels to thesame frequency allows increasing a data transmission rate, and allowsthe reception apparatus to estimate channels with ease and demultiplexthe multiplexed signals, because the symbol used for demodulation istransmitted independently of time factors.

The transmission method of the present invention inserts the symbol usedfor demodulation into a frame, and the symbol has a signal-pointamplitude at in-phase-quadrature plane greater than that by themodulation method. Thus, the symbol can withstand noises, so that anaccuracy of channel estimation is increased as well as the datatransmission quality is improved.

The transmission method of the present invention inserts symbols inframes of respective signals transmitted from a plurality oftransmitting antennas such that the symbols for estimating fluctuationsof transmission paths are placed at an identical time. Each one of thesymbols is multiplied by codes orthogonal to each other. With thismethod, multiplexing the modulation signals of a plurality of channelsto the same frequency allows increasing a data transmission rate, anduse of the codes orthogonal to each other allows the reception apparatusto isolate the symbols for estimating the fluctuations of transmissionpaths with ease. As a result, channels can be estimated with ease.

The transmission method of the present invention uses a greatertransmission power to the symbols for estimating the fluctuations oftransmission paths than the power to other symbols. With this method,the symbols used for demodulation can withstand noises, so that anaccuracy of channel estimation at the reception apparatus increases andthe quality of data transmission improves.

The transmission method of the present invention transmits modulationsignals of a plurality of channels available in the same frequency bandfrom a plurality of antennas, and only a signal transmitted from a givenantenna includes a control symbol.

The transmission method of the present invention makes both of the samephase signal and a quadrature signal in the in-phase-quadrature planetransmitted from other antennas zero when the control symbol istransmitted.

The transmission method of the present invention uses the control symbolas a symbol for time-synchronization.

The transmission method of the present invention uses the control symbolas a symbol for estimating a frequency offset.

With those features of the transmission method, multiplexing themodulation signals of a plurality of channels to the same frequencyallows increasing a data transmission rate. At the same time, thereception apparatus receives a symbol for estimatingtime-synchronization transmitted from the transmission apparatus throughone channel and a symbol for estimating a frequency offset, therebyestimating the frequency offsets for signals of a plurality of channels.As a result, a frequency offset estimation unit in the receptionapparatus can be simplified.

The transmission method of the present invention employs one of thespread spectrum communication method or the OFDM method.

The transmission method of the present invention transmits modulationsignals, undergone the spread spectrum communication method, of aplurality of channels available in the same frequency band from aplurality of antennas, and multiplexes a signal of a control channel toa modulation signal transmitted from any one of the antennas. There is atime when only this signal of the control channel is exclusivelytransmitted.

With those features, multiplexing the modulation signals of a pluralityof channels to the same frequency allows increasing a data transmissionrate. At the same time, the reception apparatus receives a symbol forestimating the time synchronization transmitted from the transmissionapparatus through one channel, thereby synchronizing signals of aplurality of channels time-wise. Thus, placement of a time-synchronizingunit at only one antenna in the reception apparatus allows obtaining thetime-synchronization, so that the circuit can be simplified.

The transmission method of the present invention transmits modulationsignals, undergone the spread spectrum communication method, of aplurality of channels available in the same frequency band from aplurality of antennas, and transmits a modulation signal of a controlchannel from only one antenna.

The transmission method of the present invention transmits a signal fromonly one antenna using an exclusive time for this transmission, andthere are a plurality of those exclusive times.

In the transmission method of the preset invention, the plurality ofthose exclusive times are available in starting the transmission.

With those features, multiplexing the modulation signals of a pluralityof channels to the same frequency allows increasing a data transmissionrate. At the same time, radio control procedures such as estimating afrequency offset, synchronization, determining a communication methodand the like can be dealt accurately with the signal transmitted fromone antenna. As a result, data quality and a transmission rate can beoptimized.

A transmission apparatus of the present invention transmits modulationsignals of a plurality of channels available in the same frequency bandfrom a plurality of antennas. The apparatus comprises a frame generatorfor inserting a symbol used for demodulation into a given channel, and amodulation signal generator for modulating a signal following the signalsupplied from the frame generator.

A transmission apparatus of the present invention includes radio unitsfor outputting radio signals to respective antennas, and the radio unitsshare a frequency source.

With those features, multiplexing the modulation signals of a pluralityof channels to the same frequency allows increasing a data transmissionrate. At the same time, sharing the frequency source makes an amount offrequency offset of the respective signals received by respectiveantenna common at the reception apparatus. Thus, an estimation of thefrequency offset of one reception signal can cover all the receptionsignals, so that an estimation circuit for the frequency offset can besimplified.

A reception apparatus of the present invention uses the symbol used fordemodulation inserted in a frame of respective channels of the receptionsignals transmitted following the transmission method of the presentinvention. The apparatus uses the foregoing symbol in the structurecomprising a transmission fluctuation estimation unit for estimating atransmission path fluctuation of a channel, and a signal processor forreceiving a transmission path fluctuation estimation signal ofrespective channels and the reception signal. The signal processor thenisolates the reception signals into signals of the respective channelsbefore outputting them.

With those features, multiplexing the modulation signals of a pluralityof channels to the same frequency allows increasing a data transmissionrate. At the same time, the symbol used for demodulation can be isolatedwith ease by the reception apparatus, or the symbol can be resistant tonoises, thereby allowing the reception apparatus to estimate channelswith ease, or increasing an accuracy of estimating channels. As aresult, the quality of data transmission is improved.

The reception apparatus of the present invention includes radio unitsfor receiving radio signals from respective antennas. The radio unitsshare a frequency source. Sharing the frequency source allows thereception apparatus to use an amount of frequency offset common to therespective signals received by the respective antennas. Thus, anestimation of the frequency offset of one reception signal can cover allthe reception signals, so that an estimation circuit for the frequencyoffset can be simplified.

The reception apparatus of the present invention comprises the followingelements:

-   -   receiving antennas for receiving signals transmitted following        the transmission method of the present invention;    -   a transmission path fluctuation estimation unit for estimating        fluctuations in a transmission path from a symbol which is        inserted into a frame of the signal to be received, where the        symbol is used for estimating fluctuations in the transmission        path; and    -   a signal processor for isolating the transmission-path        fluctuation estimation signals transmitted from the transmission        path fluctuation estimation units prepared corresponding to the        respective receiving antennas and the reception signals into        signals corresponding to the respective transmitting antennas        before outputting the signals.

With this structure, multiplexing the modulation signals of a pluralityof channels to the same frequency allows increasing a data transmissionrate. At the same time, an antenna in the best condition fordemodulation can be selected based on parameters such as a phasedifference and a received signal strength intensity. As a result, thequality of data transmission is improved and a propagation path can beestimated with ease.

The reception apparatus of the present invention comprises the followingelements:

-   -   means for receiving signals transmitted following the        transmission method of the present invention and for outputting        the signals as reception signals;    -   a transmission path fluctuation estimation unit for estimating        fluctuation in a transmission path from a symbol used for        demodulation which is inserted into a frame of a channel        included in the signal to be received; and    -   a signal processor for separating the transmission-path        fluctuation estimation signals of respective channels and the        reception signals into reception signals corresponding to the        respective channels before outputting the reception signals.

With this structure, multiplexing the modulation signals of a pluralityof channels to the same frequency allows increasing a data transmissionrate. At the same time, since the symbols used for demodulation areorthogonal to each other, the reception apparatus demultiplexes thesymbols with ease and can estimate channels.

The reception apparatus of the present invention comprises the followingelements:

-   -   means for receiving signals transmitted following the        transmission method of the present invention and outputting the        signals as reception signals;    -   a transmission path fluctuation estimation unit for estimating        fluctuations in a transmission path of channels in respective        sub-carriers from a symbol used for demodulation which is        inserted into a frame of a channel included in the signal to be        received; and    -   a signal processor for receiving the transmission-path        fluctuation estimation signals of respective channels in the        respective sub-carriers and the reception signals, then        separating those signals into reception signals of respective        channels before outputting the reception signals.

With this structure, multiplexing the modulation signals of a pluralityof channels to the same frequency allows increasing a data transmissionrate. At the same time, the symbol used for demodulation is transmittedindependently of time factors, so that the reception apparatus canestimate channels with ease and demultiplex the multiplexed signals.

The reception apparatus of the present invention receives modulationsignals transmitted according to the transmission method of the presentinvention, and comprises the following elements:

-   -   a plurality of antennas; and    -   a synchronizing unit prepared at one of the antennas for        synchronizing with the transmission apparatus using the        reception signal.

With this structure, multiplexing the modulation signals of a pluralityof channels to the same frequency allows increasing a data transmissionrate. At the same time, the reception apparatus receives the symbol forestimating the time-synchronization, where the symbol is transmittedthrough one channel from the transmission apparatus, therebysynchronizing signals time-wise of a plurality of channels. Placement ofa time-synchronizing unit at only one antenna of the reception apparatusthus achieves the time synchronization, so that the circuit can besimplified.

The reception apparatus of the present invention receives modulationsignals transmitted following the transmission method of the presentinvention, and comprises the following elements:

-   -   a plurality of antennas; and    -   a synchronizing unit prepared at each one of the respective        antennas for synchronizing with the transmission apparatus using        the reception signal.

With this structure, multiplexing the modulation signals of a pluralityof channels to the same frequency allows increasing a data transmissionrate. At the same time, the reception apparatus receives the symbol forestimating the time-synchronization, where the symbol is transmittedthrough one channel from the transmission apparatus, therebysynchronizing signals time-wise of a plurality of channels. Thereception apparatus thus obtains a timing by averagingtime-synchronization timing signals sent from the respective antennas,so that an estimation accuracy is improved.

The reception apparatus of the present invention receives modulationsignals transmitted according to the transmission method of the presentinvention, and comprises the following elements:

-   -   a plurality of antennas; and    -   a frequency offset estimation unit prepared at one of the        antennas for estimating a frequency offset between the        transmission apparatus and the reception apparatus with the        reception signal.

With this structure, multiplexing the modulation signals of a pluralityof channels to the same frequency allows increasing a data transmissionrate. At the same time, the reception apparatus receives a symbol forestimating a frequency offset, where the symbol is transmitted throughone channel from the transmission apparatus, thereby estimating thefrequency offset to signals of a plurality of channels. Placement of thefrequency offset estimation unit at only one antenna of the receptionapparatus allows estimating the frequency offset, so that the circuitcan be simplified.

The reception apparatus of the present invention receives modulationsignals transmitted according to the transmission method of the presentinvention, and comprises the following elements:

-   -   a plurality of antennas; and    -   a frequency offset estimation unit prepared corresponding to        each one of the antennas for estimating a frequency offset        between the transmission apparatus and the reception apparatus        with the reception signal.

With this structure, multiplexing the modulation signals of a pluralityof channels to the same frequency allows increasing a data transmissionrate. At the same time, the reception apparatus receives a symbol forestimating a frequency offset, where the symbol is transmitted throughone channel from the transmission apparatus, thereby estimating thefrequency offset to signals of a plurality of channels. Placement of thefrequency offset estimation unit at every antenna of the receptionapparatus can average frequency offset estimating signals, so that thefrequency offset can be accurately estimated.

The reception apparatus of the present invention detects a symbol wherea signal of only a control channel is transmitted, thereby synchronizingwith the transmission apparatus. With this feature, multiplexing themodulation signals of a plurality of channels to the same frequencyallows increasing a data transmission rate. At the same time, thereception apparatus receives a symbol for estimating thetime-synchronization, where the symbol is transmitted through onechannel from the transmission apparatus, thereby synchronizing signalstime-wise of a plurality of channels. Placement of thetime-synchronizing unit at only one antenna of the reception apparatusthus allows obtaining the time-synchronization. As a result, the circuitcan be simplified.

The reception apparatus of the present invention includes the frequencyoffset estimation unit which estimates a frequency offset from a symbolwhere the signal of only the control channel is transmitted inaccordance with the transmission method of the present invention.

With this feature, multiplexing the modulation signals of a plurality ofchannels to the same frequency allows increasing a data transmissionrate. At the same time, the frequency offset is estimated by the controlchannel, so that there is no need to insert a symbol dedicated forestimating a frequency offset. As a result, the transmission rate doesnot lower.

According to the present invention discussed above, through thetransmission method, where modulation signals of a plurality of channelsare multiplexed to the same frequency band, at the time when a symbolused for demodulation is inserted in a channel, in another channelsymbol, the same phase and quadrature signals in the in-phase-quadratureplane are made to be zero signals. With this feature, multiplexing themodulation signals of a plurality of channels to the same frequencyallows increasing a data transmission rate. At the same time, thereception apparatus can advantageously demultiplex the receptionmultiplexed modulation signals with ease.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows frame structures of channel A and channel B in accordancewith a first exemplary embodiment of the present invention.

FIG. 2 shows a structure of a transmission apparatus in accordance withthe first exemplary embodiment of the present invention.

FIG. 3 shows a structure of a modulation signal generator in accordancewith the first exemplary embodiment of the present invention.

FIG. 4 shows a point mapping of signals in in-phase-quadrature plane inaccordance with the first exemplary embodiment of the present invention.

FIG. 5 shows a structure of a reception apparatus in accordance with thefirst exemplary embodiment of the present invention.

FIG. 6 shows relations between symbols, transmission path variations andreception quadrature baseband signals in accordance with the firstexemplary embodiment of the present invention.

FIG. 7 shows frame structures of channel A and channel B in accordancewith the first exemplary embodiment of the present invention.

FIG. 8 shows a structure of a reception apparatus in accordance with asecond exemplary embodiment of the present invention.

FIG. 9 shows a structure of a reception apparatus in accordance with thesecond exemplary embodiment of the present invention.

FIG. 10 shows a transmission path variation estimation signal inaccordance with the second exemplary embodiment of the presentinvention.

FIG. 11 shows frame structures of signals in accordance with a thirdexemplary embodiment of the present invention.

FIG. 12 shows a structure of a transmission apparatus in accordance withthe third exemplary embodiment of the present invention.

FIG. 13 shows a structure of a modulation signal generator in accordancewith the third exemplary embodiment of the present invention.

FIG. 14 shows relations between pilot symbols and codes to multiply inaccordance with the third exemplary embodiment of the present invention.

FIG. 15 shows a structure of a reception apparatus in accordance withthe third exemplary embodiment of the present invention.

FIG. 16 shows a structure of a transmission path variation estimationunit in accordance with the third exemplary embodiment of the presentinvention.

FIG. 17 shows amounts of fluctuation in a transmission path along thetiming axis in accordance with the third exemplary embodiment of thepresent invention.

FIG. 18 shows a structure of a reception apparatus in accordance with afourth exemplary embodiment of the present invention.

FIG. 19 shows a structure of a reception apparatus in accordance withthe fourth exemplary embodiment of the present invention.

FIG. 20 shows a frame structure of a signal in accordance with a fifthexemplary embodiment of the present invention.

FIG. 21 shows a point mapping of signals in in-phase-quadrature (I-Q)plane in accordance with the fifth exemplary embodiment of the presentinvention.

FIG. 22 shows a structure of a modulation signal generator in accordancewith the fifth exemplary embodiment of the present invention.

FIG. 23 shows a structure of a transmission path variation estimationunit in accordance with the fifth exemplary embodiment of the presentinvention.

FIG. 24 shows frame structures of channel A and channel B in accordancewith the fifth exemplary embodiment of the present invention.

FIG. 25 shows a structure of a transmission apparatus in accordance witha sixth exemplary embodiment of the present invention.

FIG. 26 shows a structure of a reception apparatus in accordance withthe sixth exemplary embodiment of the present invention.

FIG. 27 shows distortions in transmission paths in accordance with thesixth exemplary embodiment of the present invention.

FIG. 28 shows structures of structures of a transmission path variationestimation unit and a signal processor in accordance with the sixthexemplary embodiment of the present invention.

FIG. 29 shows frame structures of signals in accordance with a seventhexemplary embodiment of the present invention.

FIG. 30 shows frame structures of signals in accordance with the seventhexemplary embodiment of the present invention.

FIG. 31 shows a transmission apparatus at a base station in accordancewith the seventh exemplary embodiment of the present invention.

FIG. 32 shows a structure of a reception apparatus at a terminal inaccordance with the seventh exemplary embodiment of the presentinvention.

FIG. 33 shows a frame structure along a time axis in accordance with aneighth exemplary embodiment of the present invention.

FIG. 34 shows a frame structure along a time axis in accordance with theeighth exemplary embodiment of the present invention.

FIG. 35 shows a structure of a modulation signal generator in accordancewith the eighth exemplary embodiment of the present invention.

FIG. 36 shows a structure of a modulation signal generator in accordancewith the eighth exemplary embodiment of the present invention.

FIG. 37 shows a structure of a reception apparatus in accordance withthe eighth exemplary embodiment of the present invention.

FIG. 38 shows a structure of a reception apparatus in accordance withthe eighth exemplary embodiment of the present invention.

FIG. 39 shows a structure of a reception apparatus in accordance withthe eighth exemplary embodiment of the present invention.

FIG. 40 shows a structure of a reception apparatus in accordance withthe eighth exemplary embodiment of the present invention.

FIG. 41 shows a structure of a reception apparatus in accordance withthe eighth exemplary embodiment of the present invention.

FIG. 42 shows a structure of a reception apparatus in accordance withthe eighth exemplary embodiment of the present invention.

FIG. 43 shows a frame structure along a time axis in accordance with aninth exemplary embodiment of the present invention.

FIG. 44 shows a frame structure along a time axis in accordance with theninth exemplary embodiment of the present invention.

FIG. 45 shows a frame structure along a time axis in accordance with theninth exemplary embodiment of the present invention.

FIG. 46 shows a structure of a modulation signal generator in accordancewith the ninth exemplary embodiment of the present invention.

FIG. 47 shows a structure of a modulation signal generator in accordancewith the ninth exemplary embodiment of the present invention.

FIG. 48 shows a structure of a modulation signal generator in accordancewith the ninth exemplary embodiment of the present invention.

FIG. 49 shows a structure of a modulation signal generator in accordancewith the ninth exemplary embodiment of the present invention.

FIG. 50 shows a frame structure along a time axis and a frequency axisin accordance with a tenth exemplary embodiment of the presentinvention.

FIG. 51 shows a frame structure along a time axis and a frequency axisin accordance with the tenth exemplary embodiment of the presentinvention.

FIG. 52 shows a structure of a reception apparatus in accordance withthe tenth exemplary embodiment of the present invention.

FIG. 53 shows a structure of a reception apparatus in accordance withthe tenth exemplary embodiment of the present invention.

FIG. 54 shows a structure of a reception apparatus in accordance withthe tenth exemplary embodiment of the present invention.

FIG. 55 shows a structure of a reception apparatus in accordance withthe tenth exemplary embodiment of the present invention.

FIG. 56 shows a structure of a reception apparatus in accordance withthe tenth exemplary embodiment of the present invention.

FIG. 57 shows a structure of a reception apparatus in accordance withthe tenth exemplary embodiment of the present invention.

FIG. 58 shows a structure of a reception apparatus in accordance with aneleventh exemplary embodiment of the present invention.

FIG. 59 shows a structure of a reception apparatus in accordance withthe eleventh exemplary embodiment of the present invention.

FIG. 60 shows a structure of a reception apparatus in accordance withthe eleventh exemplary embodiment of the present invention.

FIG. 61 shows a structure of a reception apparatus in accordance withthe eleventh exemplary embodiment of the present invention.

FIG. 62 shows a structure of a reception apparatus in accordance withthe eleventh exemplary embodiment of the present invention.

FIG. 63 shows a structure of a reception apparatus in accordance withthe eleventh exemplary embodiment of the present invention.

FIG. 64 shows a structure of a reception apparatus in accordance withthe eleventh exemplary embodiment of the present invention.

FIG. 65 shows a structure of a reception apparatus in accordance withthe eleventh exemplary embodiment of the present invention.

FIG. 66 shows a structure of a reception apparatus in accordance withthe eleventh exemplary embodiment of the present invention.

FIG. 67 shows a structure of a reception apparatus in accordance withthe eleventh exemplary embodiment of the present invention.

FIG. 68 shows a structure of a reception apparatus in accordance withthe eleventh exemplary embodiment of the present invention.

FIG. 69 shows a structure of a reception apparatus in accordance withthe eleventh exemplary embodiment of the present invention.

FIG. 70 shows a frame structure in accordance with a twelfth exemplaryembodiment of the present invention.

FIG. 71 shows a structure of an information symbol in accordance withthe twelfth exemplary embodiment of the present invention.

FIG. 72 shows a structure of an information symbol in accordance withthe twelfth exemplary embodiment of the present invention.

FIG. 73 shows a structure of an information symbol in accordance withthe twelfth exemplary embodiment of the present invention.

FIG. 74 shows a structure of a transmission apparatus in accordance withthe twelfth exemplary embodiment of the present invention.

FIG. 75 shows a structure of a reception apparatus in accordance withthe twelfth exemplary embodiment of the present invention.

FIG. 76 shows a structure of a transmission apparatus in accordance withthe twelfth exemplary embodiment of the present invention.

FIG. 77 shows a structure of a reception apparatus in accordance withthe twelfth exemplary embodiment of the present invention.

FIG. 78 shows a structure of a transmission apparatus in accordance withthe twelfth exemplary embodiment of the present invention.

FIG. 79 shows a frame structure in accordance with a thirteenthexemplary embodiment of the present invention.

FIG. 80 shows a structure of a transmission apparatus in accordance withthe thirteenth exemplary embodiment of the present invention.

FIG. 81 shows a structure of a control symbol in accordance with thethirteenth exemplary embodiment of the present invention.

FIG. 82 shows a structure of a reception apparatus in accordance withthe thirteenth exemplary embodiment of the present invention.

FIG. 83 shows a frame structure in accordance with the thirteenthexemplary embodiment of the present invention.

FIG. 84A shows a frame structure of a transmission signal from a basestation in accordance with the twelfth exemplary embodiment of thepresent invention.

FIG. 84B shows a frame structure of the transmission signal from aterminal in accordance with the twelfth exemplary embodiment of thepresent invention.

FIG. 85 shows a structure of a control symbol in accordance with thethirteenth exemplary embodiment of the present invention.

FIG. 86 shows a structure of a control symbol in accordance with thethirteenth exemplary embodiment of the present invention.

FIG. 87 shows a block diagram illustrating parts of a conventionalMIMO-OFDM system.

BEST MODE FOR PRACTICING THE INVENTION

Exemplary embodiments of the present invention are demonstratedhereinafter with reference to the accompanying drawings. In thefollowing descriptions, “antenna” does not always mean a single antenna,but “antenna” means an antenna unit which is formed of a plurality ofantennas.

Exemplary Embodiment 1

In a transmission method where modulation signals of a plurality ofchannels are multiplexed to the same frequency band, at the time when asymbol used for demodulation is inserted in a channel, in anotherchannel symbol, the same phase and quadrature signals in thein-phase-quadrature plane are made to be zero signals. The foregoingmethod and a transmission apparatus as well as a reception apparatusemployed in the method are described in this first embodiment.

FIG. 1 shows frame structure 120 of channel A and frame structure 130 ofchannel B along a time axis. Channel A has pilot symbols 101, 104, 107,guard symbols 102, 105, 108, and data symbol 103, 106. Data symbols, forinstance, have undergone QPSK (quadrature phase shift keying)modulation. Channel B has guard symbols 109, 112, 115, pilot symbols110, 113, 116, and data symbols 111, 114. Data symbols, for instance,have undergone QPSK modulation.

Pilot symbol 101 of channel A and guard symbol 109 of channel B areplaced at an identical time, and the following combinations are placedat an identical time respectively:

-   -   guard symbol 102 of channel A and pilot symbol 110 of channel B;    -   data symbol 103 of channel A and data symbol 111 of channel B;    -   pilot symbol 104 of channel A and guard symbol 112 of channel B;    -   guard symbol 105 of channel A and pilot symbol 113 of channel B;    -   data symbol 106 of channel A and data symbol 114 of channel B;    -   pilot symbol 107 of channel A and guard symbol 115 of channel B;    -   guard symbol 108 of channel A and pilot symbol 116 of channel B.

FIG. 2 shows a structure of a transmission apparatus of this firstembodiment, and the apparatus is formed of channel A transmitter 220,channel B transmitter 230, and frame structure signal generator 209.Channel A transmitter 220 is formed of modulation signal generator 202,radio unit 204, power amplifier 206, and antenna 208. Channel Btransmitter 230 is formed of modulation signal generator 212, radio unit214, power amplifier 216, and antenna 218.

Modulation signal generator 202 of channel A receives frame structuresignal 210 and transmission digital signal 201 of channel A, and outputsmodulation signal 203 in accordance with the frame structure.

Radio unit 204 of channel A receives modulation signal 203 of channel A,and outputs transmission signal 205 of channel A.

Power amplifier 206 of channel A receives transmission signal 205 ofchannel A, amplifies signal 205, and outputs transmission signal 207 ofchannel A as radio wave from antenna 208 of channel A.

Frame structure signal generator 209 outputs frame structure signal 210.

Modulation signal generator 212 of channel B receives frame structuresignal 210 and transmission digital signal 211 of channel B, and outputsmodulation signal 213 in accordance with the frame structure.

Radio unit 214 of channel B receives modulation signal 213 of channel B,and outputs transmission signal 215 of channel B.

Power amplifier 216 of channel B receives transmission signal 215 ofchannel B, amplifies signal 215, and outputs transmission signal 217 ofchannel B as radio wave from antenna 218 of channel B.

FIG. 3 shows a detailed structure of modulation signal generators 202,212 shown in FIG. 2. Data symbol modulation signal generator 302receives transmission digital signal 301 and frame structure signal 311.When frame structure signal 311 indicates a data symbol, generator 302provides signals 301 with QPSK modulation, and outputs in-phasecomponent 303 and quadrature-phase component 304 of a transmissionquadrature baseband signal of the data symbol.

Pilot symbol modulation signal generator 305 receives frame structuresignal 311. When signal 311 indicates a pilot symbol, generator 305outputs in-phase component 306 and quadrature-phase component 307 of atransmission quadrature baseband signal of the pilot symbol.

Guard symbol modulation generator 308 receives frame structure signal311. When signal 311 indicates a guard symbol, generator 308 outputsin-phase component 309 and quadrature-phase component 310 of atransmission quadrature baseband signal of the guard symbol.

In-phase component switcher 312 receives in-phase components 303, 306,309 and frame structure signal 311, then selects the in-phase componentof transmission quadrature baseband signal corresponding to a symbolindicated by frame structure signal 311, and outputs the selected one asin-phase component 313 of the selected transmission quadrature basebandsignal.

Quadrature-phase component switcher 314 receives quadrature-phasecomponents 304, 307, 310, and frame structure signal 311, then selects aquadrature-phase component of a transmission quadrature baseband signalcorresponding to a symbol indicated by frame structure signal 311, andoutputs the selected one as quadrature-phase component 315 of theselected transmission quadrature baseband signal.

Orthogonal modulator 316 receives in-phase component 313 selected,quadrature-phase component 315 selected, then provides those components313, 315 with orthogonal modulation, and outputs modulation signal 317.

FIG. 4 shows point-placement of signals of QPSK (data symbol), pilotsymbol, guard symbol, such as QPSK signal-point 401, pilot symbolsignal-point 402, and guard symbol signal-point 403.

FIG. 5 shows a structure of a reception apparatus in accordance with thefirst embodiment. Radio unit 503 receives signal 502 received by antenna501, and outputs in-phase component 504 and quadrature-phase component505 of reception quadrature baseband signal.

Transmission path variation estimation unit 506 of channel A receivesreception quadrature baseband signals 504, 505, then estimates atransmission path variation of channel A, and outputs transmission pathvariation estimation signal 507 of channel A.

Transmission path variation estimation unit 508 of channel B receivesreception quadrature baseband signals 504, 505, then estimates atransmission path variation of channel B, and outputs transmission pathvariation estimation signal 509 of channel B.

Delay unit 510 receives in-phase component 504 and quadrature-phasecomponent 505 of the reception quadrature baseband signal, and outputsin-phase component 511 and quadrature-phase component 512 of thereception quadrature baseband signal which delays by the time needed forobtaining transmission path variation estimation signals 507 and 509 ofchannel A and channel B.

Radio unit 515 receives signal 514 received by antenna 513, and outputsin-phase component 516 and quadrature-phase component 517 of thereception quadrature baseband signal.

Transmission path variation estimation unit 518 of channel A receivesreception quadrature baseband signals 516 and 517, then estimates atransmission path variation of channel A, and outputs transmission pathvariation estimation signal 519 of channel A.

Transmission path variation estimation unit 520 of channel B receivesreception quadrature baseband signals 516 and 517, then estimates atransmission path variation of channel B, and outputs transmission pathvariation estimation signal 521 of channel B.

Delay unit 522 receives in-phase component 516 and quadrature-phasecomponent 517 of the reception quadrature baseband signal, and outputsin-phase component 523 and quadrature-phase component 524 of thereception quadrature baseband signal which delays by the time needed forobtaining transmission path variation estimation signals 519 and 521 ofchannel A and channel B.

Signal processor 525 receives the following signals:

-   -   transmission path variation estimation signal 507 of channel A;    -   transmission path variation estimation signal 509 of channel B;    -   in-phase component 511 and quadrature-phase component 512 of        delayed reception quadrature baseband signal;    -   transmission path variation estimation signal 519 of channel A;    -   transmission path variation estimation signal 521 of channel B;        and    -   in-phase component 523 and quadrature-phase component 524 of        delayed reception quadrature baseband signal.

Then signal processor 525 outputs the following signals:

-   -   in-phase component 526 and quadrature-phase component 527 of        reception quadrature baseband signal of channel A; and    -   in-phase component 530 and quadrature-phase component 531 of        reception quadrature baseband signal of channel B.

Demodulator 528 receives in-phase component 526 and quadrature-phasecomponent 527 of reception quadrature baseband signal of channel A, thendemodulates those components, and outputs reception digital signal 529of channel A.

Demodulator 532 receives in-phase component 530 and quadrature-phasecomponent 531 of reception quadrature baseband signal of channel B, thendemodulates those components, and outputs reception digital signal 533of channel B.

FIG. 6 shows relation between a frame structure 620 of channel A and aframe structure 630 of channel B, symbols 601-616 of each channel atcertain times, transmission path variations 621 and 631 of channels Aand B, and reception quadrature baseband signal 632. Channel A has thefollowing symbols: pilot symbols 601, 607; guard symbols 602, 608; datasymbols 603, 604, 605, and 606. Channel B has the following symbols:guard symbols 609, 615; pilot symbols 610, 616; data symbols 611, 612,613, and 614.

Pilot symbol 601 of channel A and guard symbol 609 of channel B occur attime 0, and the following combinations occur at time 1, time 2, time 3,time 4, time 5, time 6, and time 7 respectively:

-   -   guard symbol 602 of channel A and pilot symbol 610 of channel B;    -   data symbol 603 of channel A and data symbol 611 of channel B;    -   data symbol 604 of channel A and data symbol 612 of channel B;    -   data symbol 605 of channel A and data symbol 613 of channel B;    -   data symbol 606 of channel A and data symbol 614 of channel B;    -   pilot symbol 607 of channel A and guard symbol 615 of channel B;    -   guard symbol 608 of channel A and pilot symbol 616 of channel B.

FIG. 7 shows a structure of channel A frame 720 and a structure ofchannel B frame 730 along a time axis. Channel A has the followingsymbols: pilot symbols 701, 702, 706, 707; guard symbols 703, 704, 708,709; and data symbol 705. Channel B has the following symbols: guardsymbols 710, 711, 715, 716; pilot symbols 712, 713, 717, 718; and datasymbol 714. Data symbol 705 of channel A and data symbol 714 of channelB have undergone QPSK modulation.

Pilot symbol 701 of channel A and guard symbol 710 of channel B occur atan identical time, and the following combinations occur at an identicaltime respectively:

-   -   pilot symbol 702 of channel A and guard symbol 711 of channel B;    -   guard symbol 703 of channel A and pilot symbol 712 of channel B;    -   guard symbol 704 of channel A and pilot symbol 713 of channel B;    -   data symbol 705 of channel A and data symbol 714 of channel B;    -   pilot symbol 706 of channel A and guard symbol 715 of channel B;    -   pilot symbol 707 of channel A and guard symbol 716 of channel B;    -   guard symbol 708 of channel A and pilot symbol 717 of channel B;    -   guard symbol 709 of channel A and pilot symbol 718 of channel B.

An operation of the transmission apparatus is demonstrated herein-afterwith reference to FIG. 1 through FIG. 4. In FIG. 2, frame structuresignal generator 209 outputs the information of the frame structureshown in FIG. 1 as frame structure signal 210. Modulation signalgenerator 202 of channel A receives frame structure signal 210 andtransmission digital signal 201 of channel A, then outputs modulationsignal 203 of channel A in accordance with the frame structure.Modulation signal generator 212 of channel B receives frame structuresignal 210 and transmission digital signal 211 of channel B, thenoutputs modulation signal 213 of channel B in accordance with the framestructure.

An operation of modulation signal generators 202 and 212 in the processdiscussed above is described using transmitter 220 of channel A as anexample with reference to FIG. 3.

Data symbol modulation signal generator 302 receives transmissiondigital signal 301, i.e., transmission digital signal 201 of channel Ain FIG. 2, and frame structure signal 311, i.e., frame structure signal210 in FIG. 2. When frame structure signal 311 indicates a data symbol,generator 302 provides signal 201 with QPSK modulation, and outputsin-phase component 303 and quadrature-phase component 304 of atransmission quadrature baseband signal of the data symbol.

Pilot symbol modulation signal generator 305 receives frame structuresignal 311. When signal 311 indicates a pilot symbol, generator 305outputs in-phase component 306 and quadrature-phase component 307 of atransmission quadrature baseband signal of the pilot symbol.

Guard symbol modulation signal generator 308 receives frame structuresignal 311. When signal 311 indicates a guard symbol, generator 308outputs in-phase component 309 and quadrature-phase component 310 of atransmission quadrature baseband signal of the guard symbol.

FIG. 4 shows signal-point placement of the respective symbols in anin-phase-quadrature plane of the foregoing operation. Points 401 in FIG.4 indicate the signal-points of in-phase component 303 andquadrature-phase component 304 of the transmission quadrature basebandsignal of the data symbol. Points 402 indicate the signal-points ofin-phase component 306 and quadrature-phase component 307 of thetransmission quadrature baseband signal of the pilot symbol. Point 403indicates the signal-points of in-phase component 309 andquadrature-phase component 310 of the transmission quadrature basebandsignal of the guard symbol.

In-phase component switcher 312 receives the following signals:

-   -   in-phase component 303 of data symbol transmission quadrature        baseband signal;    -   in-phase component 306 of pilot symbol transmission quadrature        baseband signal;    -   in-phase component 309 of guard symbol transmission quadrature        baseband signal; and    -   frame structure signal 311.

Switcher 312 then selects an in-phase component of a transmissionquadrature baseband signal corresponding to the symbol indicated byframe structure signal 311, and outputs the selected one as in-phasecomponent 313 of the selected transmission quadrature baseband signal.

Quadrature-phase component switcher 314 receives the following signals:

-   -   quadrature-phase component 304 of data symbol transmission        quadrature baseband signal;    -   quadrature-phase component 307 of pilot symbol transmission        quadrature baseband signal;    -   quadrature-phase component 310 of guard symbol transmission        quadrature baseband signal; and    -   frame structure signal 311.

Switcher 314 then selects a quadrature-phase component of a transmissionquadrature baseband signal corresponding to the symbol indicated byframe structure signal 311, and outputs the selected one asquadrature-phase component 315 of the selected transmission quadraturebaseband signal.

Orthogonal modulator 316 receives in-phase component 313 andquadrature-phase component 315 discussed above, then provides thosecomponents with an orthogonal modulation, and outputs modulation signal317, i.e., signal 203 shown in FIG. 2.

An operation of the reception apparatus, in particular, of transmissionpath variation estimation unit 506 of channel A, transmission pathvariation estimation unit 508 of channel B, and signal processor 525,with reference to FIG. 5 and FIG. 6.

In-phase component 504 and quadrature-phase component 505 of receptionquadrature baseband signal of the signal received by antenna 501 shownin FIG. 5 are taken as examples for description with reference to FIG.6.

In FIG. 6, at time 0 (zero), pilot symbol 601 of channel A and guardsymbol 609 of channel B are multiplexed together. Assume that in-phasecomponent 504 and quadrature-phase component 505 of the receptionquadrature baseband signal are I0 and Q0 respectively, and thetransmission path variation of channel A and that of channel B are (Ia0,Qa0) and (Ib0, Qb0), respectively. Since the transmission apparatustransmits 0 (zero) at the guard symbol of channel B, in-phase component504 and quadrature-phase component 505 of the reception quadraturebaseband signal, namely, I0 and Q0, are formed of the component of pilotsymbol 601 of channel A. Therefore, the transmission path variation ofchannel A, namely, (Ia0, Qa0) can be estimated as (I′0, Q′0) based onin-phase component 504 and quadrature-phase component 505, namely, I0and Q0.

However, the estimation of the transmission path variation of channel A,namely, (Ia0, Qa0), is not limited to the case discussed above, but apilot symbol of channel A at another time can be used for finding (Ia0,Qa0) of channel A at time 0.

In a similar manner to what is discussed above, at time 1, guard symbol602 of channel A and pilot symbol 610 of channel B are multiplexedtogether. Assume that in-phase component 504 and quadrature-phasecomponent 505 of the reception quadrature baseband signal are I1 and Q1respectively, and the transmission path variation of channel A and thatof channel B are (Ia1, Qa1) and (Ib1, Qb1) respectively. Since thetransmission apparatus transmits 0 (zero) at the guard symbol of channelA, in-phase component 504 and quadrature-phase component 505 of thereception quadrature baseband signal, namely, I1 and Q1, are formed ofthe component of pilot symbol 610 of channel B. Therefore, thetransmission path variation of channel B, namely, (Ib1, Qb1) can beestimated as (I′1, Q′1) based on in-phase component 504 andquadrature-phase component 505, namely, I1 and Q1. However, theestimation of the transmission path variation of channel B, namely,(Ib1, Qb1), is not limited to the case discussed above, but a pilotsymbol of channel B at another time can be used for finding (Ib1, Qb1)of channel B at time 1.

In a similar manner to what is discussed above, at time 6, pilot symbol607 of channel A and guard symbol 615 of channel B are multiplexedtogether. Assume that in-phase component 504 and quadrature-phasecomponent 505 of the reception quadrature baseband signal are I6 and Q6,respectively, and the transmission path variation of channel A and thatof channel B are (Ia6, Qa6) and (Ib6, Qb6). Since the transmissionapparatus transmits 0 at the guard symbol of channel B, in-phasecomponent 504 and quadrature-phase component 505 of the receptionquadrature baseband signal, namely, I6 and Q6, are formed of thecomponent of pilot symbol 607 of channel A.

Therefore, the transmission path variation of channel A, namely, (Ia6,Qa6) can be estimated as (I′6, Q′6) based on in-phase component 504 andquadrature-phase component 505, namely, I6 and Q6. However, theestimation of the transmission path variation of channel A, namely,(Ia6, Qa6), is not limited to the case discussed above, but a pilotsymbol of channel A at another time can be used for finding (Ia6, Qa6)of channel A at time 6.

In a similar manner to what is discussed above, at time 7, guard symbol608 of channel A and pilot symbol 616 of channel B are multiplexedtogether. Assume that in-phase component 504 and quadrature-phasecomponent 505 of the reception quadrature baseband signal are I7 and Q7respectively, and the transmission path variation of channel A and thatof channel B are (Ia7, Qa7) and (Ib7, Qb7). Since the transmissionapparatus transmits 0 (zero) at the guard symbol of channel A, in-phasecomponent 504 and quadrature-phase component 505 of the receptionquadrature baseband signal, namely, I7 and Q7, are formed of thecomponent of pilot symbol 610 of channel B.

Therefore, the transmission path variation of channel B, namely (Ib7,Qb7) can be estimated as (I′7, Q′7) based on in-phase component 504 andquadrature-phase component 505, namely, I7 and Q7. However, theestimation of the transmission path variation of channel B, namely (Ib7,Qb7), is not limited to the case discussed above, but a pilot symbol ofchannel B at another time can be used for finding (Ib7, Qb7) of channelB at time 7.

Assume that the transmission path variations at time 2, time 3, time 4,and time 5 are (Ia2, Qa2), (Ia3, Qa3), (Ia4, Qa4), (Ia5, Qa5). Thosevalues can be found using the estimations discussed above, i.e., (Ia0,Qa0)=(I′0, Q′0), (Ia6, Qa6)=(I′6, Q′6), by, e.g., calculation. However,in order to find (Ia2, Qa2), (Ia3, Qa3), (Ia4, Qa4), and (Ia5, Qa5),pilot symbols at another time of channel A can be used other than (Ia0,Qa0) and (Ia6, Qa6).

In a similar way to what is discussed above, assume the transmissionpath variation at time 2, time 3, time 4, and time 5 are (Ib2, Qb2),(Ib3, Qb3), (Ib4, Qb4), (Ib5, Qb5). Those values can be found using theestimations previously discussed, i.e., (Ib1, Qb1)=(I′1, Q′1), (Ib7,Qb7)=(I′7, Q′7), by, e.g., calculation. However, to find (Ib2, Qb2),(Ib3, Qb3), (Ib4, Qb4), and (Ib5, Qb5), pilot symbols at another time ofchannel B can be used other than (Ib1, Qb1) and (Ib7, Qb7).

The preparation discussed above allows transmission path variationestimation unit 506 of channel A to output, e.g., the foregoing (Ia0,Qa0), (Ia1, Qa1), (Ia2, Qa2), (Ia3, Qa3), (Ia4, Qa4), (Ia5, Qa5), (Ia6,Qa6), and (Ia7, Qa7) as transmission path variation estimation signals507 of channel A.

In a similar way to the case of channel A, transmission path variationestimation unit 508 of channel B outputs, e.g., the foregoing (Ib0,Qb0), (Ib1, Qb1), (Ib2, Qb2), (Ib3, Qb3), (Ib4, Qb4), (Ib5, Qb5), (Ib6,Qb6), and (Ib7, Qb7) as transmission path variation estimation signals509 of channel B.

The foregoing description expresses the transmission path variation in(I, Q); however, the distortion can be expressed in power and phase, sothat estimation signals 507 and 509 can be expressed in power and phase.

In a similar way to what is discussed above, transmission path variationestimation unit 518 of channel A receives in-phase component 516 andquadrature-phase component 517 of a reception quadrature baseband signalof a signal received by antenna 513 shown in FIG. 5. Then estimationunit 518 outputs estimation signal 519 of channel A. Estimation unit 520of channel B outputs estimation signal 521 of channel B.

Signal processor 525 receives the following signals:

-   -   transmission path variation estimation signal 507 of channel A;    -   transmission path variation estimation signal 509 of channel B;    -   transmission path variation estimation signal 519 of channel A;    -   transmission path variation estimation signal 521 of channel B;    -   in-phase component 511 and quadrature-phase component 512 of        delayed reception quadrature baseband signal; and    -   in-phase component 523 and quadrature-phase component 524 of        delayed reception quadrature baseband signal.

Signal processor 525 carries out matrix calculations with those knownsignals, so that unknown signals such as a reception quadrature basebandsignal of channel A and that of channel B can be found. Signal processor525 thus outputs those unknown signals as in-phase component 526 andquadrature-phase component 527 of the reception quadrature basebandsignal of channel A, and in-phase component 530 and quadrature-phasecomponent 531 of that of channel B. As a result, modulation signals ofchannels A and B can be demultiplexed from each other, which allowsdemodulation.

In this embodiment, an accuracy of demultiplexing the modulation signalsbetween channel A and channel B at the reception apparatus depends on aquality of the pilot symbol received. Thus, stronger resistance of thepilot symbol to noise increases the accuracy of demultiplexing betweenthe modulation signals of channel A and channel B. As a result, thequality of data received can be improved. The way of achieving this goalis described hereinafter.

In FIG. 4, assume that the pilot symbol has amplitude Ap from theorigin, and QPSK has the greatest signal-point amplitude Aq from theorigin. In this status, the relation of Ap>Aq increases the resistanceto noise of the pilot symbol, so that the accuracy of demultiplexing themodulation signals of channel A from those of channel B. As a result,the quality of data received can be improved.

As shown in FIG. 7, the frame of channel A includes pilot symbols 701,702, and 706, 707. The frame of channel B includes pilot symbol 712,713, and 717, 718. Those pilot symbols are placed in series along thetime axis, so that the pilot symbols become stronger to noises. Thus theaccuracy of the demultiplexing the modulation signals between channel Aand channel B. As a result, the quality of data received is improved.This is not limited to two symbols in series as shown in FIG. 7.

In this embodiment, the number of channels to be multiplexed are two;however, other numbers can be applicable to the embodiment. The framestructure is not limited to what is shown in FIG. 1, FIG. 6 or FIG. 7.The pilot symbol is taken as an example for demultiplexing the channels;however, other symbols as long as they are used for demodulation can bealso applicable. In this case, the symbols used for demodulationinclude, e.g., pilot symbol, unique word, synchronous symbol, preamblesymbol, control symbol, tail symbol, control symbol, known PSK (phaseshift keying) modulation symbol, and PSK modulation symbol added withdata.

A modulation method of the data symbol is not limited to QPSKmodulation, but respective channels can undergo different modulations.On the other hand, all the channels can use the spread spectrumcommunication method. The spread spectrum communication method cancoexist with the other methods.

The structure of the transmission apparatus of this embodiment is notlimited to what is shown in FIG. 2 or FIG. 3, and when the number ofchannels increase, elements 201 through 208 shown in FIG. 2 are addedaccordingly.

The structure of the reception apparatus of this embodiment is notlimited to what is shown in FIG. 5, and when the number of channelsincrease, the number of channel estimation units increases accordingly.

The expression of “antenna” in the previous description does not alwaysmean a single antenna, but “antenna” can mean an antenna unit which isformed of a plurality of antennas.

In this embodiment, the transmission path variation estimation unit ofeach channel estimates the transmission path variation; however, anestimation of transmission path fluctuation instead of distortion canachieve a similar advantage to what is discussed in this embodiment. Inthis case, a transmission path fluctuation estimation unit forestimating fluctuations of the transmission path is used instead of thedistortion estimation unit. The output signal should be a fluctuationestimation signal accordingly.

According to the first embodiment discussed above, in a transmissionmethod for transmitting modulation signals of a plurality of channels tothe same frequency band, at the time when a symbol used for demodulationis inserted in a channel, in another channel symbol, both of the samephase signal and a quadrature signal in the in-phase-quadrature planeare made to be zero signals. Use of this method, a transmissionapparatus and a reception apparatus to which this method is applicable,allows the transmission rate of data to increase, and allows thereception apparatus to demultiplex the multiplexed modulation signalwith ease.

Exemplary Embodiment 2

In this second embodiment, a reception apparatus is described. Thereception apparatus comprising the following elements:

-   -   a received signal strength intensity estimation unit for        estimating a reception received signal strength intensity of a        signal received by respective antennas and outputting an        estimation signal of the reception received signal strength        intensity of the reception signal;    -   a phase difference estimation unit for receiving a transmission        path variation estimation signal of a channel of the respective        antennas, finding a phase difference of the transmission path        variation estimation signal between the respective antennas, and        outputting a phase difference signal; and    -   a signal selection unit for receiving a reception quadrature        baseband signal of the respective antennas, a transmission path        variation estimation signal of each channel of the respective        antennas, a reception electric field estimation signal of the        reception signal, the phase difference signal, then selecting        the reception quadrature baseband signal and the transmission        path variation estimation signal for isolating signals of the        respective channels from the reception signal, and outputting        the signals selected.

The description refers to the case as an example where the transmissionapparatus shown in FIG. 2 transmits the modulation signals of the framestructure shown in FIG. 1 demonstrated in the first embodiment.

FIG. 8 shows a structure of the reception apparatus in accordance withthe second embodiment. Radio unit 803 of this apparatus receives signal802 received by antenna 801, and outputs in-phase component 804 andquadrature-phase component 805 of the reception quadrature basebandsignal.

Transmission path variation estimation unit 806 of channel A receivesin-phase component 804 and quadrature-phase component 805 of thereception quadrature baseband signal. Then estimation unit 806 operates,e.g., in a similar way to estimation unit 506 of channel A shown in FIG.5 of the first embodiment, and outputs transmission path variationestimation signal 807 of channel A.

Transmission path variation estimation unit 808 of channel B receivesin-phase component 804 and quadrature-phase component 805 of thereception quadrature baseband signal. Then estimation unit 808 operates,e.g., in a similar way to estimation unit 506 of channel A shown in FIG.5 of the first embodiment, and outputs transmission path variationestimation signal 809 of channel B.

Delay unit 810 receives in-phase component 804 and quadrature-phasecomponent 805 of the reception quadrature baseband signal, and outputsin-phase component 811 and quadrature-phase component 812 of thereception quadrature baseband signal which delays by the time needed forobtaining transmission path variation estimation signals 807 and 809 ofchannel A and channel B.

Radio unit 815 receives signal 814 received by antenna 813, and outputsin-phase component 816 and quadrature-phase component 817 of thereception quadrature baseband signal.

Transmission path variation estimation unit 818 of channel A receivesin-phase component 816 and quadrature-phase component 817 of thereception quadrature baseband signal. Then estimation unit 818 operates,e.g., in a similar way to estimation unit 506 of channel A shown in FIG.5 of the first embodiment, and outputs transmission path variationestimation signal 819 of channel A.

Transmission path variation estimation unit 820 of channel B receivesin-phase component 816 and quadrature-phase component 817 of thereception quadrature baseband signal. Then estimation unit 820 operates,e.g., in a similar way to estimation unit 506 of channel A shown in FIG.5 of the first embodiment, and outputs transmission path variationestimation signal 821 of channel B.

Delay unit 822 receives in-phase component 816 and quadrature-phasecomponent 817 of the reception quadrature baseband signal, and outputsin-phase component 823 and quadrature-phase component 824 of thereception quadrature baseband signal which delays by the time needed forobtaining transmission path variation estimation signals 819 and 821 ofchannel A and channel B.

Radio unit 827 receives signal 826 received by antenna 825, and outputsin-phase component 828 and quadrature-phase component 829 of receptionquadrature baseband signal.

Transmission path variation estimation unit 830 of channel A receivesin-phase component 828 and quadrature-phase component 829 of thereception quadrature baseband signal. Then estimation unit 830 operates,e.g., in a similar way to estimation unit 506 of channel A shown in FIG.5 of the first embodiment, and outputs transmission path variationestimation signal 831 of channel A.

Transmission path variation estimation unit 832 of channel B receivesin-phase component 828 and quadrature-phase component 829 of thereception quadrature baseband signal. Then estimation unit 832 operates,e.g., in a similar way to estimation unit 506 of channel A shown in FIG.5 of the first embodiment, and outputs transmission path variationestimation signal 833 of channel B.

Delay unit 834 receives in-phase component 828 and quadrature-phasecomponent 829 of the reception quadrature baseband signal, and outputsin-phase component 835 and quadrature-phase component 836 of thereception quadrature baseband signal which delays by the time needed forobtaining transmission path variation estimation signals 831 and 833 ofchannel A and channel B.

Radio unit 839 receives signal 838 received by antenna 837, and outputsin-phase component 840 and quadrature-phase component 841 of receptionquadrature baseband signal.

Transmission path variation estimation unit 842 of channel A receivesin-phase component 840 and quadrature-phase component 841 of thereception quadrature baseband signal. Then estimation unit 842 operates,e.g., in a similar way to estimation unit 506 of channel A shown in FIG.5 of the first embodiment, and outputs transmission path variationestimation signal 843 of channel A.

Transmission path variation estimation unit 844 of channel B receivesin-phase component 840 and quadrature-phase component 841 of thereception quadrature baseband signal. Then estimation unit 844 operates,e.g., in a similar way to estimation unit 506 of channel A shown in FIG.5 of the first embodiment, and outputs transmission path variationestimation signal 845 of channel B.

Delay unit 846 receives in-phase component 840 and quadrature-phasecomponent 841 of the reception quadrature baseband signal, and outputsin-phase component 847 and quadrature-phase component 848 of thereception quadrature baseband signal which delays by the time needed forobtaining transmission path variation estimation signals 843 and 845 ofchannel A and channel B.

Received signal strength intensity estimation unit 849 receivesreception signals 802, 814, 826, 838, then estimates the receptionreceived signal strength intensity of the foregoing respective signals,and outputs the estimated values as reception received signal strengthintensity estimation signal 850.

Phase difference estimation unit 851 receives transmission pathvariation estimation signals 807, 819, 831, 843 of channel A, then findsrespective phase differences such as a phase difference between signals807 and 819 in the in-phase-quadrature plane, and outputs the phasedifference as phase difference estimation signal 852 of channel A.

In a similar way to what is done by estimation unit 851, phasedifference estimation unit 853 receives transmission path variationestimation signals 809, 821, 833, 845 of channel B, then findsrespective phase differences such as a phase difference between signals809 and 821 in the in-phase-quadrature plane, and outputs the phasedifference as phase difference estimation signal 854 of channel B.

Signal selection unit 855 receives the following signals:

-   -   transmission path variation estimation signal 807 of channel A;    -   transmission path variation estimation signal 809 of channel B;    -   in-phase component 811 and quadrature-phase component 812 of        delayed reception quadrature baseband signal;    -   transmission path variation estimation signal 819 of channel A;    -   transmission path variation estimation signal 821 of channel B;    -   in-phase component 823 and quadrature-phase component 824 of        delayed reception quadrature baseband signal;    -   transmission path variation estimation signal 831 of channel A;    -   transmission path variation estimation signal 833 of channel B;    -   in-phase component 835 and quadrature-phase component 836 of        delayed reception quadrature baseband signal;    -   transmission path variation estimation signal 843 of channel A;    -   transmission path variation estimation signal 845 of channel B;    -   in-phase component 847 and quadrature-phase component 848 of        delayed reception quadrature baseband signal;    -   received signal strength intensity estimation signal 850;    -   phase difference estimation signal 852 of channel A; and    -   phase difference estimation signal 854 of channel B;

Then signal selection unit 855 selects a group of signals supplied fromthe antenna, which can most accurately demultiplex channel A signalsfrom channel B signals, out of received signal strength intensityestimation signal 850, phase difference estimation signal 852 of channelA, and phase difference estimation signal 854 of channel B. Signalselection unit 855 outputs signal groups 856 and 857.

The signal group here refers to, e.g., transmission path variationestimation signal 807 and estimation signal 809 of channel B estimatedfrom the signal received by antenna 801, in-phase component 811 andquadrature-phase component 812 of the delayed reception quadraturebaseband signal.

Signal processor 858 receives signal groups 856, 857, and operates in asimilar way to signal processor 525 shown in FIG. 5 of the firstembodiment. Signal processor 858 outputs in-phase component 859,quadrature-phase component 860 of the reception quadrature basebandsignal of channel A as well as in-phase component 861, quadrature-phasecomponent of the reception quadrature baseband signal 862 of channel B.

Demodulator 863 receives in-phase component 859 and quadrature-phasecomponent 860 of the reception quadrature baseband signal of channel A,and outputs reception digital signal 864 of channel A.

Demodulator 865 receives in-phase component 861 and quadrature-phasecomponent 862 of the reception quadrature baseband signal of channel B,and outputs reception digital signal 866 of channel B.

FIG. 9 shows a structure of the reception apparatus in accordance withthe second embodiment, and the elements operating in a similar way tothose shown in FIG. 8 have the same reference marks.

Received signal strength intensity estimation unit 901 receives thefollowing signals:

-   -   in-phase component 804 and quadrature-phase component 805 of the        reception quadrature baseband signal;    -   in-phase component 816 and quadrature-phase component 817 of the        reception quadrature baseband signal:    -   in-phase component 828 and quadrature-phase component 829 of the        reception quadrature baseband signal; and    -   in-phase component 840 and quadrature-phase component 841 of the        reception quadrature baseband signal.

Then estimation unit 901 estimates the reception received signalstrength intensity of the foregoing respective components, and outputsreception received signal strength intensity estimation signal 850.

FIG. 10 shows transmission path variation estimation signals of achannel in accordance with the second embodiment. The following foursignals are mapped in FIG. 10:

-   -   transmission path variation estimation signal 1001 of a channel        of a signal received by antenna 801, and expressed in (I801,        Q801);    -   transmission path variation estimation signal 1002 of a channel        of a signal received by antenna 813, and expressed in (I813,        Q813);    -   transmission path variation estimation signal 1003 of a channel        of a signal received by antenna 825, and expressed in (I825,        Q825);    -   transmission path variation estimation signal 1004 of a channel        of a signal received by antenna 837, and expressed in (I837,        Q837);

Next, an operation of the reception apparatus, in particular of phasedifference estimation unit 851 and signal selection unit 855, isdemonstrated hereinafter with reference to FIGS. 8 and 10.

Assume that phase difference estimation unit 851 receives signal 1001,signal 1002, signal 1003 and signal 1004 in FIG. 10 as transmission pathvariation estimation signals 807, 819, 831, and 843 of channel Arespectively. In this case, find the phase difference between (I801,Q801) and (I813, Q813) in I-Q plane. In a similar way to this, find thephase difference between the following combinations in I-Q plane: (I801,Q801) and (I825, Q825); (I801, Q801) and (I837, Q837); (I813, Q813) and(I825, Q825); (I813, Q813) and (I837, Q837). Then phase differenceestimation unit 851 outputs phase difference estimation signal 852 ofchannel A. Phase difference estimation unit 853 outputs phase differenceestimation signal 854 of channel B in a similar way to what is discussedabove.

Next, an operation of signal selection unit 855 is demonstrated: Phasedifference estimation signal 852 of channel A takes a value ranging from0 to pi (π). In other words, the foregoing respective phase differencesbetween (I801, Q801) and (I813, Q813); (I801, Q801) and (I825, Q825);(I801, Q801) and (I837, Q837); (I813, Q813) and (I825, Q825); (I813,Q813) and (I837, Q837) take a value ranging from 0 to pi (π). Forinstance, assume that the phase difference between (I801, Q801) and(I813, Q813) is θ, find an absolute value of θ, and find absolute valuesof each one of the phase differences.

In a similar way, determine whether or not phase difference estimationsignal 854 of channel B has correlation.

Signal selection unit 855 selects an optimum antenna 2 system out ofphase difference estimation signals 852, 854 of channels A, B supplied.A method of this selection is demonstrated hereinafter.

For instance, assume that a phase difference of channel A of signalsreceived by antenna 801 and antenna 813 is 0 (zero) and that of channelB is also 0. At this time, it is prepared that the signals received byantennas 801 and 813 should not be selected as signal groups 856, 857.On the other hand, assume that a phase difference of channel A ofsignals received by antenna 801 and antenna 813 is 0 (zero) and that ofchannel B is pi (π). At this time, it is prepared that the signalsreceived by antennas 801 and 813 should be selected as signal groups856, 857.

Place signal 802 received by antenna 801, signal 814 by antenna 813,signal 826 by antenna 825, and signal 838 by antenna 837 in descendingorder of reception received signal strength intensity with receivedsignal strength intensity estimation signal 850. Then select the signalshaving stronger electric field intensities as signal groups 856, 857.

As such, optimum signal groups are selected on a priority base using aphase difference or a reception received signal strength intensity, thenthe selected ones are output as signal groups 856, 857. For instance,the phase difference between a transmission path variation of channel Aof antenna 801 and that of antenna 813 does not correlate with the phasedifference between a transmission path variation of channel B of antenna801 and that of antenna 813. The reception received signal strengthintensity of antenna 801 and that of antenna 813 are stronger than thoseof other antennas. Then transmission path variation estimation signal807 of channel A, variation estimation signal 809 of channel B, in-phasecomponent 811 and quadrature-phase component 812 of the delayedreception orthogonal are output as signal group 856. Transmission pathvariation estimation signal 819 of channel A, variation estimationsignal 821 of channel B, in-phase component 823 and quadrature-phasecomponent 824 of the delayed reception orthogonal are output as signalgroup 857.

FIG. 9 has a structure of the received signal strength intensityestimation unit different from that shown in FIG. 8. Reception electricfield estimation unit 901 of FIG. 9 differs from that of FIG. 8 in thefollowing point: Estimation unit 901 finds reception received signalstrength intensity from in-phase component 804 and quadrature-phasecomponent 805 of the reception quadrature baseband signal. In a similarmanner, estimation unit 901 finds the respective field intensity fromin-phase component 816 and quadrature-phase component 817, from in-phasecomponent 828 and quadrature-phase component 829, and from in-phasecomponent 840 and quadrature-phase component 841.

In the descriptions discussed above, the frame structure of thetransmission signal shown in FIG. 1 is taken as an example; however,this second embodiment is not limited to the example. Use of twochannels as the number of channels in the descriptions does not limitthis embodiment, and an increase of channels will increase the number oftransmission path variation estimation units. Each channel can undergo adifferent modulation method from each other. On the other hand, all thechannels can use the spread spectrum communication method. The spreadspectrum communication method can coexist with the other methods.

Not less than four antennas installed in the reception apparatus canassure the better reception sensitivity. The expression of “antenna” inthe previous description does not always mean a single antenna, but“antenna” can mean an antenna unit which is formed of a plurality ofantennas.

According to the second embodiment discussed above, the receptionapparatus comprises the following elements:

-   -   a received signal strength intensity estimation unit for        estimating a reception received signal strength intensity of a        signal received by respective antennas and outputting an        estimation signal of the reception received signal strength        intensity of the reception signal;    -   a phase difference estimation unit for receiving a transmission        path variation estimation signal of a channel of the respective        antennas, finding a phase difference of the transmission path        variation estimation signal, and outputting a phase difference        signal; and    -   a signal selection unit for receiving a reception quadrature        baseband signal of the respective antennas, a transmission path        variation estimation signal of each channel of the respective        antennas, a reception electric field estimation signal of the        reception signal, the phase difference signal, then selecting        the reception quadrature baseband signal and the transmission        path variation estimation signal for demultiplexing signals of        the respective channels from the reception signal, and        outputting the signals selected.

The foregoing structure allows the reception apparatus to demultiplexthe multiplexed signals with accuracy.

Exemplary Embodiment 3

The third embodiment describes a transmission method, which handles thefollowing frame structure of signals transmitted from respectiveantennas:

-   -   a symbol for estimating transmission path variation is inserted        into the frame;    -   the symbols is multiplied by a code;    -   the symbols of the respective antennas are placed at an        identical time; and    -   the codes of the respective antennas are orthogonal to each        other.

The third embodiment also describes a transmission apparatus and areception apparatus both used in the foregoing transmission method.

FIG. 11 shows frame structure 1120 in accordance with spread spectrumcommunication method A, and frame structure 1130 in accordance withspread spectrum communication method B. Pilot symbols 1101, 1103, 1105of spread spectrum communication method A are multiplied by a code. Datasymbols 1102, 1104 of spread spectrum communication method A aremultiplied by a code.

Pilot symbols 1106, 1108, 1110 of spread spectrum communication method Bare multiplied by a code. Data symbols 1107, 1109 of spread spectrumcommunication method B are multiplied by a code.

Pilot symbol 1101 of communication method A and pilot symbol 1106 ofcommunication method B occur at an identical time. In the same manner,the following combinations occur at an identical time:

-   -   data symbol 1102 of method A and data symbol 1107 of method B;    -   pilot symbol 1103 of method A and pilot symbol 1108 of method B;    -   data symbol 1104 of method A and data symbol 1109 of method B;        and    -   pilot symbol 1105 of method A and pilot symbol 1110 of method B

FIG. 12 shows a structure of the transmission apparatus in accordancewith this third embodiment, and the apparatus comprises transmissionunit 1220 of spread spectrum communication method A, transmission unit1230 of spread spectrum communication method B, and frame structuresignal generator 1217.

Transmission unit 1220 of method A is formed of modulation signalgenerator 1202, radio unit 1204, power amplifier 1206, and antenna 1208.Transmission unit 1230 of method B is formed of modulation signalgenerator 1210, radio unit 1212, power amplifier 1214, and antenna 1216.Frame structure signal generator 1217 outputs the information about theframe structure shown in FIG. 11 as frame structure signal 1218.

Modulation signal generator 1202 of method A receives transmissiondigital signal 1201 of spread spectrum transmission method A and framestructure signal 1218, then outputs modulation signal 1203 of method Ain accordance with the frame structure.

Radio unit 1204 of method A receives modulation signal 1203, thenoutputs transmission signal 1205 of method A.

Power amplifier 1206 of method A receives transmission signal 1205,amplifies it, then outputs the amplified signal as transmission signal1207 from antenna 1208 in the form of radio wave.

Modulation signal generator 1210 of method B receives transmissiondigital signal 1209 of spread spectrum transmission method B and framestructure signal 1218, then outputs modulation signal 1211 of method Bin accordance with the frame structure.

Radio unit 1212 of method B receives modulation signal 1211, thenoutputs transmission signal 1213 of method B.

Power amplifier 1214 of method B receives transmission signal 1213,amplifies it, then outputs the amplified signal as transmission signal1215 from antenna 1216 in the form of radio wave.

FIG. 13 shows a structure of modulation signal generators 1202, 1210shown in FIG. 12 of the third embodiment. Pilot symbol modulation signalgenerator 1301 receives code Cpa(t) 1302 for a pilot symbol, andmultiplies the pilot symbol by code Cpa(t) 1302, then outputs in-phasecomponent 1303 and quadrature-phase component 1304 of a transmissionquadrature baseband signal of the pilot symbol.

Primary modulation unit 1306 receives transmission digital signal 1305,then outputs in-phase component 1307 and quadrature-phase component 1308of the quadrature baseband signal of channel 0 undergone the primarymodulation.

Spread unit 1309 receives in-phase component 1307 and quadrature-phasecomponent 1308 of the quadrature baseband signal of channel 0 undergonethe primary modulation, code C0a(t) 1310 for channel 0, frame structuresignal 1320, then multiplies in-phase component 1307, quadrature-phasecomponent 1308 and code C0a(t) 1310 based on the information about framestructure 1320, and outputs in-phase component 1311 and quadrature-phasecomponent 1312 of a transmission quadrature baseband signal of channel0.

Primary modulation unit 1313 receives transmission digital signal 1305,then outputs in-phase component 1314 and quadrature-phase component 1315of the quadrature baseband signal of channel 1 undergone the primarymodulation.

Spread unit 1316 receives in-phase component 1314 and quadrature-phasecomponent 1315 of the quadrature baseband signal of channel 1 undergonethe primary modulation, code C1a(t) 1317 for channel 1, frame structuresignal 1320, then multiplies in-phase component 1314, quadrature-phasecomponent 1315 and code C1a(t) 1317 based on the information about theframe structure 1320, and outputs in-phase component 1318 andquadrature-phase component 1319 of a transmission quadrature basebandsignal of channel 1.

Adding unit 1321 receives in-phase component 1311 of the transmissionquadrature baseband signal of channel 0 and in-phase component 1318 ofthat of channel 1, and adds component 1311 and component 1318 together,then outputs the added in-phase component 1322.

Adding unit 1323 receives quadrature-phase component 1312 of thetransmission quadrature baseband signal of channel 0 and in-phasecomponent 1319 of that of channel 1, and adds component 1312 andcomponent 1319 together, then outputs the added quadrature-phasecomponent 1324.

In-phase component switcher 1325 receives in-phase component 1303 of thepilot symbol transmission quadrature baseband signal 1303, addedin-phase component 1322 and frame structure signal 1320, then selectsin-phase component 1303 and added in-phase component 1322 based on theinformation about frame structure 1320, and outputs in-phase component1326 of the selected transmission quadrature baseband signal.

Quadrature-phase component switcher 1327 receives quadrature-phasecomponent 1304 of the pilot symbol transmission quadrature basebandsignal, added quadrature-phase component 1324 and frame structure signal1320, then selects quadrature-phase component 1304 and addedquadrature-phase component 1324 based on the information about framestructure 1320, and outputs quadrature-phase component 1328 of theselected transmission quadrature baseband signal.

Orthogonal modulation unit 1329 receives in-phase component 1326 andquadrature-phase component 1328 of the selected transmission quadraturebaseband signal, then provides the input with orthogonal modulation, andoutputs modulation signal 1330.

FIG. 14 shows a relation between a pilot symbol and a code to bemultiplied to the pilot symbols in pilot-symbol structure 1420 ofspread-spectrum communication method A and in pilot-symbol structure1430 of method B. Spread code 1401 of method A at time 0 is expressed asCpa(0), and spread code 1402 of method A at time 1 is expressed asCpa(1). The following codes are expressed in the same manner:

-   -   code 1403 of method A at time 2 as Cpa(2);    -   code 1404 of method A at time 3 as Cpa(3);    -   code 1405 of method A at time 4 as Cpa(4);    -   code 1406 of method A at time 5 as Cpa(5);    -   code 1407 of method A at time 6 as Cpa(6); and    -   code 1408 of method A at time 7 as Cpa(7).

Time 0-time 7 form one cycle of spread code Cpa.

In a similar manner to the spread codes of method A, spread codes ofmethod B are expressed as follows:

-   -   code 1409 of method B at time 0 as Cpb(0);    -   code 1410 of method B at time 1 as Cpb(1);    -   code 1411 of method B at time 2 as Cpb(2);    -   code 1412 of method B at time 3 as Cpb(3);    -   code 1413 of method B at time 4 as Cpb(4);    -   code 1414 of method B at time 5 as Cpb(5);    -   code 1415 of method B at time 6 as Cpb(6); and    -   code 1416 of method B at time 7 as Cpb(7).

Time 0-time 7 form one cycle of spread code Cpb.

FIG. 15 shows a structure of the reception apparatus in accordance withthe third embodiment. The elements operating in the same way as those inFIG. 5 have the same reference marks.

Transmission path variation estimation unit 1501 of spread-spectrumcommunication method A receives in-phase component 504 andquadrature-phase component 505 of the reception quadrature basebandsignal. Then estimation unit 1501 estimates transmission-path distortionof method A, and outputs transmission path estimation signal 1502 ofmethod A.

Transmission path variation estimation unit 1503 of spread-spectrumcommunication method B receives in-phase component 504 andquadrature-phase component 505 of the reception quadrature basebandsignal. Then estimation unit 1503 estimates transmission-path distortionof method B, and outputs transmission path estimation signal 1504 ofmethod B.

Transmission path variation estimation unit 1505 of spread-spectrumcommunication method A receives in-phase component 516 andquadrature-phase component 517 of the reception quadrature basebandsignal. Then estimation unit 1505 estimates transmission-path distortionof method A, and outputs transmission path estimation signal 1506 ofmethod A.

Transmission path variation estimation unit 1507 of spread-spectrumcommunication method B receives in-phase component 516 andquadrature-phase component 517 of the reception quadrature basebandsignal. Then estimation unit 1507 estimates transmission-path distortionof method B, and outputs transmission path estimation signal 1508 ofmethod B.

Signal processor 1509 receives the following signals:

-   -   transmission path variation estimation signal 1502 of method A;    -   transmission path variation estimation signal 1504 of method B;    -   in-phase component 511 and quadrature-phase component 512 of        delayed reception quadrature baseband signal;    -   transmission path variation estimation signal 1506 of method A;    -   transmission path variation estimation signal 1508 of method B;        and    -   in-phase component 523 and quadrature-phase component 524 of        delayed reception quadrature baseband signal.

Then signal processor 1509 outputs the following signals:

-   -   in-phase component 1510 and quadrature-phase component 1511 of        reception quadrature baseband signal of method A; and    -   in-phase component 1512 and quadrature-phase component 1513 of        reception quadrature baseband signal of method B.

Demodulator 1514 of spread spectrum communication method A receivesin-phase component 1510 and quadrature-phase component 1511 of receptionquadrature baseband signal of method A, and outputs reception-digitalsignal group 1515 of method A.

Demodulator 1516 of spread spectrum communication method B receivesin-phase component 1512 and quadrature-phase component 1513 of receptionquadrature baseband signal of method B, and outputs reception-digitalsignal group 1517 of method B.

FIG. 16 a structure of transmission path variation estimation units1501, 1505 of spread-spectrum communication method A and distortionestimation units 1503, 1507 of method B, both shown in FIG. 15.

Pilot-symbol inverse spread unit 1603 receives in-phase component 1601and quadrature-phase component 1602 of the reception quadrature basebandsignal, and spread-code 1604, and outputs in-phase component 1605 andquadrature-phase component 1606 of the pilot symbol of the receptionquadrature baseband signal undergone the inverse spread.

Transmission path variation estimation unit 1607 receives in-phasecomponent 1605 and quadrature-phase component 1606, and outputstransmission path variation estimation signal 1608.

FIG. 17 shows frame structure 1710 and transmission path variationamount 1720 along a time axis. Pilot symbol 1701 and transmission pathvariation (I0, Q0) occur at time 0 (zero). In the same manner, followingcombinations occur at respective times:

-   -   pilot symbol 1702 and transmission path variation (I1, Q1) at        time 1    -   pilot symbol 1703 and transmission path variation (I2, Q2) at        time 2    -   pilot symbol 1704 and transmission path variation (I3, Q3) at        time 3    -   pilot symbol 1705 and transmission path variation (I4, Q4) at        time 4    -   pilot symbol 1706 and transmission path variation (I5, Q5) at        time 5    -   pilot symbol 1707 and transmission path variation (I6, Q6) at        time 6.

An operation of the transmission apparatus is demonstrated hereinafterwith reference to FIG. 11-FIG. 14. Structures of pilot symbol 1101 ofcommunication method A and pilot symbol 1106 of method B, both occurringat the same time, are described with reference to FIG. 14.

FIG. 14 shows a structure of one pilot symbol. Pilot symbol 1101 ofspread-spectrum communication method A shown in FIG. 11 is multiplied bycode Cpa, and formed of, e.g., spread codes 1401, 1402, 1403, 1404,1405, 1406, 1407, and 1408. In a similar way, pilot symbol 1106 ofspread-spectrum communication method B shown in FIG. 11 is multiplied bycode Cpb, and formed of, e.g., spread codes 1409, 1410, 1411, 1412,1413, 1414, 1415, and 1416. Spread code Cpa multiplied to the pilotsymbol of method A is orthogonal to spread code Cpb multiplied to thepilot symbol of method B.

Next, the operation of the transmission apparatus is demonstrated. InFIG. 12, frame structure signal generator 1217 outputs the informationabout the frame structure shown in FIG. 11 as frame structure signal1218. Modulation signal generator 1202 of method A receives transmissiondigital signal 1201 of spread spectrum transmission method A and framestructure signal 1218, then outputs modulation signal 1203 of method Ain accordance with the frame structure. Modulation signal generator 1210of method B receives transmission digital signal 1209 of spread spectrumtransmission method B and frame structure signal 1218, then outputsmodulation signal 1211 of method B in accordance with the framestructure.

Operations of modulation signal generators 1202 and 1210 aredemonstrated with reference to FIG. 13. At a transmitter ofspread-spectrum communication method A, pilot-symbol transmission signalgenerator 1301 shown in FIG. 13 receives code 1302 for the pilot symboland frame structure signal 1320. Then generator 1301 outputs, e.g.,in-phase component 1303 and quadrature-phase component 1304 of a pilotsymbol transmission quadrature baseband signal in accordance with thestructure of the pilot symbol of communication method A shown in FIG.14.

In a similar way to the foregoing transmitter, at a transmitter ofspread-spectrum communication method B, pilot-symbol transmission signalgenerator 1301 shown in FIG. 13 receives code 1302 for the pilot symboland frame structure signal 1320. Then generator 1301 outputs, e.g.,in-phase component 1303 and quadrature-phase component 1304 of a pilotsymbol transmission quadrature baseband signal in accordance with thestructure of the pilot symbol of communication method B shown in FIG.14.

As such, the pilot symbol of communication method A is orthogonal to thespread code of the pilot symbol of communication method B.

Next, an operation of the reception apparatus is demonstrated withreference to FIG. 15-FIG. 17. Antenna 501 shown in FIG. 15 receivessignal 502 in which spread-spectrum communication methods A and B aremixed, and radio unit 503 outputs in-phase component 504 andquadrature-phase component 505, in which methods A and B are mixed, of areception quadrature baseband signal.

Operations of transmission path variation estimation unit 1501 of methodA and estimation unit 1503 of method B are demonstrated with referenceto FIG. 16. Estimation unit 1501 of method A operates as follows:Pilot-symbol inverse-spread unit 1603 in FIG. 16 receives in-phasecomponent 1601 and quadrature-phase component 1602 of the receptionquadrature baseband signal, in which methods A and B are mixed, andspread code 1604 for the pilot symbol of method A. Then inverse-spreadunit 1603 detects pilot symbols in in-phase component 1601 andquadrature-phase component 1602, and provides the detected pilot symbolswith the inverse-spread using spread-code 1604. Finally, inverse-spreadunit 1603 outputs in-phase component 1605 and quadrature-phase component1606 undergone the inverse spread.

In the foregoing operation, the component of method B in the pilotsymbol of in-phase component 1601 and quadrature-phase component 1602can be removed by the inverse-spread because the code of method A isorthogonal to the code of method B.

Transmission path variation estimation unit 1607 is described withreference to FIG. 17. Transmission path variations (I0, Q0) and (I6, Q6)of the pilot symbol in FIG. 17 are found using in-phase component 1605and quadrature-phase component 1606 of the reception quadrature basebandsignal of the pilot symbol undergone the inverse-spread. Thentransmission path variations (I1, Q1), (I2, Q2), (I3, Q3), (I4, Q4), and(I5, Q5) of data symbol are found using distortions (I0, Q0) and (I6,Q6) of the pilot symbol. Those distortions are output as transmissionpath variation estimation signal 1608.

In a similar way to what is discussed above, transmission path variationestimation unit 1503 of method B outputs estimation signal 1504 fromreception signal 502 in which methods A and B are mixed. Distortionestimation unit 1505 of method A and estimation unit 1507 of method Boutput transmission variation estimation signal 1506 of method A andestimation signal 1508 of method B respectively from reception signal514 in which methods A and B are mixed.

In the foregoing descriptions, the transmission path variation isexpressed in (I, Q); however the distortion can be expressed in power orphase, so that the distortions expressed in power and phase can beoutput as variation estimation signals 1502, 1506 of method A, andsignals 1506, 1508 of method B.

The structures and operations discussed above allow demultiplexing themodulation signals of spread-spectrum communication method A from thoseof method B, so that the signals can be demodulated.

In this embodiment, an accuracy of demultiplexing the modulation signalsbetween channel A and channel B at the reception apparatus depends on aquality of the pilot symbol received. Thus, stronger resistance of thepilot symbol to noise increases the accuracy of demultiplexing themodulation signals of channel A from channel B. As a result, the qualityof data received can be improved. A greater transmission power to thepilot symbols than that to the data symbols increases the noiseresistance of the pilot symbols, so that the accuracy of demultiplexingthe modulation signals of spread-spectrum communication method A frommethod B increases. As a result, the quality of reception data can beimproved.

In this third embodiment, two methods of spread-spectrum communicationmethods are multiplexed; however, the present invention is not limitedto two methods. The present invention is not limited to the framestructures shown in FIGS. 11, 14, and 16. The transmission pathvariation can be estimated using the pilot symbol as an example;however, other symbols can be used for this purpose as long as they canestimate distortions. Spread-spectrum communication methods A and B usetwo channels for multiplexing; however, it is not limited to twochannels only.

The structure of the transmission apparatus in accordance with the thirdembodiment is not limited to what is shown in FIG. 12 or FIG. 13, andwhen the number of spread-spectrum communication methods increases, thenumber of sections formed of elements 1201-1208 shown in FIG. 12increases accordingly. When the number of channels increases, the numberof sections formed of elements 1306 and 1309 shown in FIG. 13 increasesaccordingly.

The structure of the reception apparatus in accordance with the thirdembodiment is not limited to what is shown in FIG. 15, and when thenumber of spread-spectrum communication methods increases, the number ofdistortion estimation units increases accordingly.

The expression of “antenna” in the previous description does not alwaysmean a single antenna, but “antenna” can mean an antenna unit which isformed of a plurality of antennas.

According to the third embodiment discussed above, the transmissionmethod handles the following frame structure of a signal transmittedfrom respective antenna:

-   -   a symbol for estimating transmission path variation is inserted        into the frame;    -   the symbol is multiplied by a code;    -   the symbols of the respective antennas are arranged at an        identical time; and    -   the codes of the respective antennas are orthogonal to each        other.

The third embodiment also uses the transmission apparatus and thereception apparatus in the foregoing transmission method. In thissystem, multiplexing modulation signals of a plurality of channels tothe same frequency band increases the data transmission rate, and allowsthe reception apparatus to demultiplex the multiplexed modulation signalwith ease.

Exemplary Embodiment 4

The fourth exemplary embodiment demonstrates a reception apparatuscomprising the following elements:

-   -   a received signal strength intensity estimation unit for        receiving a modulation signal of a spread-spectrum communication        method transmitted to the same frequency band from respective        transmission antennas, then estimating a reception received        signal strength intensity of the signal received by respective        antennas, and outputting an estimation signal of the reception        received signal strength intensity of the reception signal;    -   a phase difference estimation unit for receiving a transmission        path variation estimation signal of a spread-spectrum        communication method of the respective antennas, finding a phase        difference of the transmission path variation estimation signals        of the spread-spectrum communication method between the        respective antennas, and outputting a phase difference signal;        and    -   a signal selection unit for receiving a reception quadrature        baseband signal of the respective antennas, the transmission        path variation estimation signals of respective spread-spectrum        communication methods of the respective antennas, the reception        received signal strength intensity estimation signal of the        reception signal, the phase difference signal, then selecting        the reception quadrature baseband signal and the transmission        path variation estimation signal for isolating signals of the        respective methods from the reception signal, and outputting the        signals selected.

The description of this fourth embodiment takes the case as an example,where the modulation signal having the frame structure shown in FIG. 11is transmitted by the transmission apparatus shown in FIG. 12 and usedin the third exemplary embodiment.

FIG. 18 shows a structure of a reception apparatus in accordance withthe fourth embodiment. The elements operating in a similar way to thosein FIG. 8 have the same reference marks.

Transmission path variation estimation unit 1801 of spread-spectrumcommunication method A receives in-phase component 804 andquadrature-phase component 805 of the reception quadrature basebandsignal. Then estimation unit 1801 operates, e.g., in a similar way toestimation unit 1501 of method A shown in FIG. 15 of the thirdembodiment, and outputs transmission path variation estimation signal1802 of method A.

Transmission path variation estimation unit 1803 of spread-spectrumcommunication method B receives in-phase component 804 andquadrature-phase component 805 of the reception quadrature basebandsignal. Then estimation unit 1803 operates, e.g., in a similar way toestimation unit 1501 of method A shown in FIG. 15 of the thirdembodiment, and outputs transmission path variation estimation signal1804 of method B.

Delay unit 1805 receives in-phase component 804 and quadrature-phasecomponent 805 of the reception quadrature baseband signal, and outputsin-phase component 1806 and quadrature-phase component 1807 of thereception quadrature baseband signal which delays by the time needed forobtaining transmission path variation estimation signals 1802 and 1804of method A and method B.

Transmission distortion estimation unit 1808 of method A receivesin-phase component 816 and quadrature-phase component 817 of thereception quadrature baseband signal. Then estimation unit 1808operates, e.g., in a similar way to estimation unit 1501 of the samemethod A shown in FIG. 15 of the third embodiment, and outputstransmission path variation estimation signal 1809 of method A.

Transmission path variation estimation unit 1810 of method B receivesin-phase component 816 and quadrature-phase component 817 of thereception quadrature baseband signal. Then estimation unit 1810operates, e.g., in a similar way to estimation unit 1501 of method Ashown in FIG. 15 of the third embodiment, and outputs transmission pathvariation estimation signal 1811 of method B.

Delay unit 1812 receives in-phase component 816 and quadrature-phasecomponent 817 of the reception quadrature baseband signal, and outputsin-phase component 1813 and quadrature-phase component 1814 of thereception quadrature baseband signal which delays by the time needed forobtaining transmission path variation estimation signals 1809 and 1811of method A and method B.

Transmission distortion estimation unit 1815 of method A receivesin-phase component 828 and quadrature-phase component 829 of thereception quadrature baseband signal. Then estimation unit 1815operates, e.g., in a similar way to estimation unit 1501 of channel Ashown in FIG. 15 of the third embodiment, and outputs transmission pathvariation estimation signal 1816 of method A.

Transmission path variation estimation unit 1817 of method B receivesin-phase component 828 and quadrature-phase component 829 of thereception quadrature baseband signal. Then estimation unit 1817operates, e.g., in a similar way to estimation unit 1501 of method Ashown in FIG. 15 of the third embodiment, and outputs transmission pathvariation estimation signal 1818 of method B.

Delay unit 1819 receives in-phase component 828 and quadrature-phasecomponent 829 of the reception quadrature baseband signal, and outputsin-phase component 1820 and quadrature-phase component 1821 of thereception quadrature baseband signal which delays by the time needed forobtaining transmission path variation estimation signals 1816 and 1818of method A and method B.

Transmission distortion estimation unit 1822 of method A receivesin-phase component 840 and quadrature-phase component 841 of thereception quadrature baseband signal. Then estimation unit 1822operates, e.g., in a similar way to estimation unit 1501 of method Ashown in FIG. 15 of the third embodiment, and outputs transmission pathvariation estimation signal 1823 of method A.

Transmission path variation estimation unit 1824 of method B receivesin-phase component 840 and quadrature-phase component 841 of thereception quadrature baseband signal. Then estimation unit 1824operates, e.g., in a similar way to estimation unit 1501 of channel Ashown in FIG. 15 of the third embodiment, and outputs transmission pathvariation estimation signal 1825 of method B.

Delay unit 1826 receives in-phase component 840 and quadrature-phasecomponent 841 of the reception quadrature baseband signal, and outputsin-phase component 1827 and quadrature-phase component 1828 of thereception quadrature baseband signal which delays by the time needed forobtaining transmission path variation estimation signals 1823 and 1825of method A and method B.

Phase difference estimation unit 1829 receives transmission pathvariation estimation signals 1802, 1809, 1816, 1823 of method A, thenfinds respective phase differences such as a phase difference betweensignals 1802 and 1809 in the in-phase-quadrature plane, and outputs thephase difference as phase difference estimation signal 1830 of method A.

In a similar way to what is done by estimation unit 1829, phasedifference estimation unit 1831 receives transmission path variationestimation signals 1804, 1811, 1818, 1825 of method B, then findsrespective phase differences such as a phase difference between signals1804 and 1811 in the in-phase-quadrature plane, and outputs the phasedifferences as phase difference estimation signal 1832 of method B.

Signal selection unit 1833 receives the following signals:

-   -   transmission path variation estimation signal 1802 of method A;    -   transmission path variation estimation signal 1804 of method B;    -   in-phase component 1806 and quadrature-phase component 1807 of        delayed reception quadrature baseband signal;    -   transmission path variation estimation signal 1809 of method A;    -   transmission path variation estimation signal 1811 of method B;    -   in-phase component 1813 and quadrature-phase component 1814 of        delayed reception quadrature baseband signal;    -   transmission path variation estimation signal 1816 of method A;    -   transmission path variation estimation signal 1818 of method B;    -   in-phase component 1820 and quadrature-phase component 1821 of        delayed reception quadrature baseband signal;    -   transmission path variation estimation signal 1823 of method A;    -   transmission path variation estimation signal 1825 of method B;    -   in-phase component 1827 and quadrature-phase component 1828 of        delayed reception quadrature baseband signal;    -   received signal strength intensity estimation signal 850;    -   phase difference estimation signal 1830 of method A; and    -   phase difference estimation signal 1832 of method B;

Then signal selection unit 1833 selects a group of signals supplied fromthe antenna, which can most accurately isolate method A signals frommethod B signals, out of received signal strength intensity estimationsignal 850, phase difference estimation signal 1830 of method A, andphase difference estimation signal 1832 of method B. Signal selectionunit 1833 then outputs signal groups 1834 and 1835.

The signal group here refers to, e.g., transmission path variationestimation signal 1802 of method A, estimation signal 1804 of method B,in-phase component 1806 and quadrature-phase component 1807 of thedelayed reception quadrature baseband signal of the signal received byantenna 801.

Signal processor 1836 receives signal groups 1834, 1835, and operates ina similar way to signal processor 1509 shown in FIG. 15 of the thirdembodiment. Signal processor 1836 outputs in-phase component 1837,quadrature-phase component 1838 of the reception quadrature basebandsignal of method A as well as in-phase component 1839, quadrature-phasecomponent of the reception quadrature baseband signal 1840 of method B.

Demodulator 1841 of spread-spectrum communication method A receivesin-phase component 1837 and quadrature-phase component 1838 of thereception quadrature baseband signal of method A, and outputs receptiondigital signal 1842 of method A.

Demodulator 865 of spread-spectrum communication method B receivesin-phase component 1839 and quadrature-phase component 1840 of thereception quadrature baseband signal of method B, and outputs receptiondigital signal 1844 of method B.

FIG. 19 shows a structure of the reception apparatus in accordance withthis exemplary embodiment, and the elements operating in a similar wayto those shown in FIGS. 8 and 18 have the same reference marks.

FIG. 10 shows transmission path variation estimation signals of aspread-spectrum communication method in accordance with the fourthembodiment. The following four signals are mapped in FIG. 10:

-   -   transmission path variation estimation signal 1001 of a signal        of a spread-spectrum communication method received by antenna        801, and expressed in (I801, Q801);    -   transmission path variation estimation signal 1002 of a signal        of a spread-spectrum communication method received by antenna        813, and expressed in (I813, Q813);    -   transmission path variation estimation signal 1003 of a signal        of a spread-spectrum communication method received by antenna        825, and expressed in (I825, Q825);    -   transmission path variation estimation signal 1004 of a signal        of a spread-spectrum method received by antenna 837, and        expressed in (I837, Q837);

Next, an operation of the reception apparatus, in particular operationsof phase difference estimation unit 1829 and signal selection unit 1831,is demonstrated hereinafter with reference to FIGS. 1 and 18.

Assume that phase difference estimation unit 1829 receives signal 1001,signal 1002, signal 1003 and signal 1004 shown in FIG. 10 astransmission path variation estimation signals 1802, 1809, 1816, and1823 of method A respectively. In this case, find the phase differencebetween (I801, Q801) and (I813, Q813) in I-Q plane. In a similar way tothis, find the phase difference between the following combinations inI-Q plane: (I801, Q801) and (I825, Q825); (I801, Q801) and (I837, Q837);(I813, Q813) and (I825, Q825); (I813, Q813) and (I837, Q837). Then phasedifference estimation unit 851 outputs phase difference estimationsignal 852 of method A. Phase difference estimation unit 1831 outputsphase difference estimation signal 1832 of method B in a similar way towhat is discussed above.

Next, an operation of signal selection unit 1833 is demonstrated: Phasedifference estimation signal 1830 of method A takes a value ranging from0 to pi (π). In other words, the foregoing respective phase differencesbetween (I801, Q801) and (I813, Q813); (I801, Q801) and (I825, Q825);(I801, Q801) and (I837, Q837); (I813, Q813) and (I825, Q825); (I813,Q813) and (I837, Q837) take a value ranging from 0 to pi (π). Forinstance, assume that the phase difference between (I801, Q801) and(I813, Q813) is θ, find an absolute value of θ, and find absolute valuesof each one of the phase differences.

In a similar way, determine whether or not phase difference estimationsignal 1832 of method B has correlation.

Signal selection unit 1833 selects optimum antenna system 2 based onphase difference estimation signals 1830, 1832 of spread-spectrumcommunication methods A, B supplied. A method of this selection isdemonstrated hereinafter.

For instance, assume that a phase difference of method A of signalsreceived by antenna 801 and antenna 813 is 0 (zero) and that of method Bis also 0. At this time, it is prepared that the signals received byantennas 801 and 813 should not be selected as signal groups 856, 857.On the other hand, assume that a phase difference of method A of signalsreceived by antenna 801 and antenna 813 is 0 (zero) and that of method Bis pi (π). At this time, it is prepared that the signals received byantennas 801 and 813 should be selected as signal groups 1834, 1835.

Place signal 802 received by antenna 801, signal 814 by antenna 813,signal 826 by antenna 825, and signal 838 by antenna 837 in descendingorder of reception received signal strength intensity with electricfield estimation signal 850, then select the signals having strongerreceived signal strength intensity as signal groups 856, 857.

As such, optimum signal groups are selected on a priority base using aphase difference or a reception received signal strength intensity, thenthe selected ones are output as signal groups 1834, 1835. For instance,the phase difference between a transmission path variation of method Aof antenna 801 and that of antenna 813 does not correlate with the phasedifference between a transmission path variation of method B of antenna801 and that of antenna 813. The reception received signal strengthintensity of antenna 801 and that of antenna 813 are stronger than thoseof other antennas. Then transmission path variation estimation signal1802 of method A, variation estimation signal 1804 of method B, in-phasecomponent 1806 and quadrature-phase component 1807 of the delayedreception orthogonal are output as signal group 1834. Transmission pathvariation estimation signal 1809 of method A, variation estimationsignal 1811 of method B, in-phase component 1813 and quadrature-phasecomponent 1814 of the delayed reception orthogonal are output as signalgroup 1835.

FIG. 19 shows a structure of the received signal strength intensityestimation unit different from that shown in FIG. 18. Reception receivedsignal strength intensity estimation unit 901 of FIG. 19 differs fromthat of FIG. 18 in the following point: Estimation unit 901 findsreception received signal strength intensity from in-phase component 804and quadrature-phase component 805 of the reception quadrature basebandsignal. In a similar manner, estimation unit 901 finds the respectivefield intensity from in-phase component 816 and quadrature-phasecomponent 817, from in-phase component 828 and quadrature-phasecomponent 829, and from in-phase component 840 and quadrature-phasecomponent 841.

In the descriptions discussed above, the frame structure of thetransmission signal shown in FIG. 11 is taken as an example; however,this embodiment is not limited to the example. Use of twospread-spectrum communication methods as the number of communicationmethods in the descriptions does not limit this embodiment, and anincrease of the methods will increase the number of transmission pathvariation estimation units. Method A and method B undergo multiplexingof two channels; however, the present invention is not limited totwo-channels.

Not less than four antennas installed in the reception apparatus assurethe better reception sensitivity. The expression of “antenna” in theprevious description does not always mean a single antenna, but“antenna” can mean an antenna unit which is formed of a plurality ofantennas.

As discussed above, the fourth exemplary embodiment has referred to thereception apparatus comprising the following elements:

-   -   a received signal strength intensity estimation unit for        receiving a modulation signal of a spread-spectrum communication        method transmitted to the same frequency band from respective        transmission antennas, then estimating a reception received        signal strength intensity of the signal received by respective        antennas, and outputting an estimation signal of the reception        received signal strength intensity of the reception signal;    -   a phase difference estimation unit for receiving a transmission        path variation estimation signal of a spread-spectrum        communication method of the respective antennas, finding a phase        difference of the transmission path variation estimation signal        of the spread-spectrum communication method between the        respective antennas, and outputting a phase difference signal;    -   and    -   a signal selection unit for receiving a reception quadrature        baseband signal of the respective antennas, a transmission path        variation estimation signal of respective spread-spectrum        communication methods of the respective antennas, a reception        electric field estimation signal of the reception signal, and        the phase difference signal, then selecting the reception        quadrature baseband signal and the transmission path variation        estimation signal for isolating signals of the respective        methods from the reception signal, and outputting the signals        selected.

The foregoing structure allows the reception apparatus to demultiplex amultiplexed signal with accuracy.

Exemplary Embodiment 5

The fifth exemplary embodiment describes the transmission method oftransmitting modulation signals of a plurality of channels from aplurality of antennas to the same frequency band. More particularly, asymbol used for demodulation to be inserted into a channel is formed ofa plurality of sequential symbols, and each one of symbols used fordemodulation of respective channels is placed at the same time andorthogonal to each other. The fifth embodiment also describes atransmission apparatus and a reception apparatus to be used in theforegoing transmission method.

FIG. 20 shows frame structure 2020 of channel A and frame structure 2030of channel B along a time axis. Frame structure 2020 includes pilotsymbols 2001, 2002, 2003, 2004, 2006, 2007, 2008, 2009, and data symbol2005. Frame structure 2030 includes pilot symbols 2010, 2011, 2012,2013, 2015, 2016, 2017, 2018, and data symbol 2014.

FIG. 21 shows a placement of signal points of the pilot symbols ofchannels A and B in in-phase-quadrature (I-Q) plane, and signal points2101 and 2102 indicate the pilot symbols.

FIG. 2 shows a structure of the transmission apparatus in accordancewith the fifth embodiment.

FIG. 22 shows a detailed structure of modulation signal generators 202,212. Data-symbol modulation signal generator 2202 receives transmissiondigital signal 2201, frame structure signal 2208. When frame structuresignal 2208 indicates a data symbol, generator 2202 provides signals2201 with, e.g., QPSK modulation, and outputs in-phase component 2203and quadrature-phase component 2204 of a transmission quadraturebaseband signal of the data symbol.

Pilot symbol modulation signal generator 2205 receives frame structuresignal 2208. When signal 2208 indicates a pilot symbol, generator 2205outputs in-phase component 2206 and quadrature-phase component 2207 of atransmission quadrature baseband signal of the pilot symbol.

In-phase component switcher 2209 receives in-phase components 2203, 2206and frame structure signal 2208, then selects the in-phase component oftransmission quadrature baseband signal corresponding to a symbolindicated by frame structure signal 2208, and outputs the selected oneas in-phase component 2210 of the selected transmission quadraturebaseband signal.

Quadrature-phase component switcher 2211 receives quadrature-phasecomponents 2204, 2207 and frame structure signal 2208, then selects aquadrature-phase component of a transmission quadrature baseband signalcorresponding to a symbol indicated by frame structure signal 2208, andoutputs the selected one as quadrature-phase component 2212 of theselected transmission quadrature baseband signal.

Orthogonal modulator 2213 receives in-phase component 2210 selected,quadrature-phase component 2212 selected, then provides those components2210, 2212 with orthogonal modulation, and outputs modulation signal2214.

FIG. 5 shows a structure of the reception apparatus in accordance withthis fifth embodiment.

FIG. 17 shows amounts of transmission path variation along a time axis.Transmission path variation (I0, Q0) 1701 at time 0 (zero) is found bycorrelation calculation. In the same manner, following combinations arefound at respective times by correlation calculations:

-   -   data symbol 1702 and transmission path variation (I1, Q1) at        time 1    -   data symbol 1703 and transmission path variation (I2, Q2) at        time 2    -   data symbol 1704 and transmission path variation (I3, Q3) at        time 3    -   data symbol 1705 and transmission path variation (I4, Q4) at        time 4    -   data symbol 1706 and transmission path variation (I5, Q5) at        time 5    -   data symbol 1707 and transmission path variation (I6, Q6) at        time 6.

FIG. 23 shows a structure of transmission path variation estimationunits 506, 518 of channel A and estimation units 508, 520 of channel Bshown in FIG. 5.

Pilot symbol correlation calculation unit 2303 receives in-phasecomponent 2301, quadrature-phase component 2302 of a receptionquadrature baseband signal, and pilot-symbol series 2304, then outputsin-phase component 2305, quadrature-phase component 2306 of thereception quadrature baseband signal of the pilot symbols undergone thecorrelation calculations.

Transmission path variation estimation unit 2307 receives in-phasecomponent 2305 and quadrature-phase component 2306, and outputstransmission-path variation estimation signal 2308.

The transmission method in accordance with this fifth embodiment isdemonstrated hereinafter with reference to FIGS. 20 and 21.

The signal point of pilot symbol 2001 of channel A at time 0 is placedat point 2101 (1, 1) in FIG. 21. The signal point of pilot symbol 2002of channel A at time 1 is placed at point 2101 (1, 1) in FIG. 21. Thesignal point of pilot symbol 2003 of channel A at time 2 is placed atpoint 2101 (1, 1) in FIG. 21. The signal point of pilot symbol 2004 ofchannel A at time 3 is placed at point 2101 (1, 1) in FIG. 21.

The signal point of pilot symbol 2010 of channel B at time 0 is placedat point 2101 (1, 1) in FIG. 21. The signal point of pilot symbol 2011of channel B at time 1 is placed at point 2101 (1, 1) in FIG. 21. Thesignal point of pilot symbol 2012 of channel B at time 2 is placed atpoint 2102 (−1, −1) in FIG. 21. The signal point of pilot symbol 2013 ofchannel B at time 3 is placed at point 2102 (−1, −1) in FIG. 21.

In a similar way to what discussed above, the signal point of pilotsymbol 2006 is placed at the same place as that of pilot symbol 2001.The signal points of pilot symbols 2007, 2008, 2009 are placed at thesame places of pilot symbols 2002, 2003, 2004 respectively. In the samemanner, the signal points of pilot symbols 2015, 2016, 2017, 2018 areplaced at the same places of pilot symbols 2010, 2011, 2012, 2013respectively.

As such, sequential pilot symbols 2001, 2002, 2003, 2004 of channel Ahas correlation of 0 (zero) with sequential pilot symbols 2010, 2011,2012, 2013 of channel B.

Next, an operation of the transmission apparatus is demonstratedhereinafter with reference to FIG. 2 and FIG. 22.

In FIG. 2, frame structure signal generator 209 outputs the informationof the frame structure shown in FIG. 20 as frame structure signal 210.Modulation signal generator 202 of channel A receives frame structuresignal 210 and transmission digital signal 201 of channel A, thenoutputs modulation signal 203 of channel A in accordance with the framestructure. Modulation signal generator 212 of channel B receives framestructure signal 210 and transmission digital signal 211 of channel B,then outputs modulation signal 213 of channel B in accordance with theframe structure.

An operation of modulation signal generators 202 and 212 at the processdiscussed above is described using transmitter 220 of channel A as anexample with reference to FIG. 22.

Data symbol modulation signal generator 2202 receives transmissiondigital signal 2201, i.e., transmission digital signal 201 of channel Ain FIG. 2, and frame structure signal 2208, i.e., frame structure signal210 in FIG. 2. When frame structure signal 208 indicates a data symbol,generator 2202 provides signal 2201 with QPSK modulation, and outputsin-phase component 2203 and quadrature-phase component 2204 of atransmission quadrature baseband signal of the data symbol.

Pilot symbol modulation signal generator 2205 receives frame structuresignal 2208. When signal 2208 indicates a pilot symbol, generator 2205outputs in-phase component 2206 and quadrature-phase component 2207 of atransmission quadrature baseband signal of the pilot symbol.

In-phase component switcher 312 receives the following signals:

-   -   in-phase component 2203 of a data symbol transmission quadrature        baseband signal;    -   in-phase component 2206 of a pilot symbol transmission        quadrature baseband signal; and    -   frame structure signal 2208.

Switcher 312 then selects an in-phase component of the transmissionquadrature baseband signal corresponding to the symbol indicated byframe structure signal 2208, and outputs the selected one as in-phasecomponent 2210 of the selected transmission quadrature baseband signal.

Quadrature-phase component switcher 2211 receives the following signals:

-   -   quadrature-phase component 2204 of data symbol transmission        quadrature baseband signal;    -   quadrature-phase component 2207 of pilot symbol transmission        quadrature baseband signal; and    -   frame structure signal 2208.

Switcher 2211 then selects a quadrature-phase component of atransmission quadrature baseband signal corresponding to the symbolindicated by frame structure signal 2208, and outputs the selected oneas quadrature-phase component 2212 of the selected transmissionorthogonal base-band.

Orthogonal modulator 2213 receives in-phase component 2210 andquadrature-phase component 2212 discussed above, then provides thosecomponents with an orthogonal modulation, and outputs modulation signal2214, i.e., signal 203 shown in FIG. 2.

Next, an operation of the reception apparatus, in particular, operationsof transmission path variation estimation unit 506 of channel A,transmission path variation estimation unit 508 of channel B, and signalprocessor 525, with reference to FIG. 5 and FIG. 23. Estimation unit 506of channel A is taken as an example for the description purpose.

Pilot correlation calculation unit 2303 shown in FIG. 23 receivesin-phase component 2301, quadrature-phase component 2302 of a receptionquadrature signal, in which channel A and channel B are mixed with eachother, received by antenna 501, and pilot-symbol series 2304 of channelA, then detects pilot symbols in in-phase component 2301 andquadrature-phase component 2302. Calculation unit 2303 then calculatescorrelation between the pilot symbol section detected and pilot-symbolseries 2304, and outputs in-phase component 2305, quadrature-phasecomponent 2306 undergone the correlation calculation.

The pilot-symbol series of channel A can be formed of the in-phasecomponent and the quadrature-phase component. In such a case, channel Bcomponent of the pilot symbol in in-phase component 2301 andquadrature-phase component 2302 of the reception quadrature basebandsignal can be removed by the correlation calculation because thepilot-symbol series of channel A is orthogonal to the pilot-symbolseries of channel B.

Transmission path variation estimation unit 2307 is described withreference to FIG. 17. Distortions (I0, Q0) and (I6, Q6) in FIG. 17 arefound by pilot-symbol correlation calculation unit 2303. Data-symboltransmission path variations (I1, Q1), (I2, Q2), (I3, Q3), (I4, Q4),(I5, Q5) are found from distortions (I0, Q0) and (I6, Q6), thenestimation unit 2307 outputs those distortions as transmission pathvariation estimation signal 2308.

In a similar way to estimation unit 506 of channel A, transmission pathvariation estimation unit 508 of channel B outputs transmission pathvariation estimation signal 509 of reception signal 502 in which channelA and channel B are mixed with each other. Estimation unit 518 ofchannel A and estimation unit 520 of channel B output variationestimation signal 519 of channel A and variation estimation signal 521of channel B respectively from reception signal 514 where channel A andchannel B are mixed.

The foregoing description expresses the transmission path variation in(I, Q); however, the distortion can be expressed in power and phase, sothat estimation signals 507, 519 of channel A and estimation signal 509,521 of channel B can be expressed in power and phase.

The foregoing structure and operation allow the reception apparatus todemultiplex the modulation signals of channel A from those of channel B,so that the signals can be demodulated.

In this fifth embodiment, the number of channels to be multiplexed istwo, however, the embodiment is not limited to two channels, and notlimited to the frame structure shown in FIG. 20. The transmission pathvariation can be estimated using the pilot symbol as an example, andother symbols can be used for this purpose as long as they can estimatethe distortion.

The expression of “antenna” in the previous description does not alwaysmean a single antenna, but “antenna” can mean an antenna unit which isformed of a plurality of antennas.

The structure of the transmission apparatus of this embodiment is notlimited to what is shown in FIG. 2 or FIG. 22, and when the number ofchannels increase, the structure formed of elements 201 through 208shown in FIG. 2 is added accordingly.

The structure of the reception apparatus of this embodiment is notlimited to what is shown in FIG. 5 or FIG. 23, and when the number ofchannels increase, the number of channel estimation units increasesaccordingly.

As discussed above, the fifth exemplary embodiment describes thetransmission method of transmitting modulation signals of a plurality ofchannels from a plurality of antennas to the same frequency band. Moreparticularly, a symbol used for demodulation to be inserted into achannel is formed of a plurality of sequential symbols, and each one ofsymbols used for demodulation of respective channels is placed at thesame time and orthogonal to each other. The fifth embodiment alsodescribes the transmission apparatus and the reception apparatus to beused in the foregoing transmission method. The foregoing transmissionmethod, transmission apparatus and reception apparatus allowmultiplexing modulation signals of a plurality of channels to the samefrequency band. Through this operation, the transmission rate of datacan be increased, at the same time, the symbol used for demodulation hasresistance to noises, so that an accuracy of channel estimation in thereception apparatus is increased. As a result, transmission quality ofdata is improved.

Exemplary Embodiment 6

The sixth exemplary embodiment describes the transmission method whichtransmits modulation signals of a plurality of channels to the samefrequency band from a plurality of antennas. More particularly, in thismethod, at the time when a symbol used for demodulation is inserted in achannel having a frame structure in accordance with OFDM method and inthe symbols of other channels of sub-carriers, both of the same phasesignal and a quadrature signal in the in-phase-quadrature plane are madeto be zero signals. The sixth embodiment also describes a transmissionapparatus and a reception apparatus to be used in the foregoingtransmission method.

FIG. 4 shows a placement of signal points in on-phase-quadrature (I-Q)plane. FIG. 24 shows examples of frame structure 2410 of channel A andframe structure 2420 of channel B along a frequency axis. Framestructure 2410 includes pilot symbol 2401 and data symbol 2402. As shownin FIG. 24, at time 0 of channel A, sub-carrier 2 is assigned as pilotsymbol. At this time, assume that channel B has a symbol of (I, Q)=(0,0). As such, assume that at a certain time and a certain frequency, whenchannel A shows a pilot symbol, channel B has a symbol of (I, Q)=(0, 0).On the contrary, when channel B shows a pilot symbol, channel A has asymbol of (I, Q)=(0, 0).

FIG. 25 shows a structure of the transmission apparatus in accordancewith the sixth embodiment, and the transmission apparatus is formed ofchannel A transmitter 2530, channel B transmitter 2540 and framestructure signal generator 2521.

Transmitter 2530 of channel A comprises serial-parallel converter 2502,inverse discrete Fourier transformer 2504, radio unit 2506, poweramplifier 2508, and antenna 2510.

Transmitter 2540 of channel B comprises serial-parallel converter 2512,inverse discrete Fourier transformer 2514, radio unit 2516, poweramplifier 2518, and antenna 2520.

Frame structure signal generator 2521 outputs the information of theframe structure as frame structure signal 2522.

Serial-parallel converter 2502 of channel A receives transmissiondigital signal 2501 of channel A and frame structure signal 2522, andoutputs parallel signal 2503 of channel A in accordance with the framestructure.

Inverse discrete Fourier transformer 2504 of channel A receives parallelsignal 2503, and outputs signal 2505 undergone the inverse discreteFourier transformation of channel A.

Radio unit 2506 of channel A receives signal 2505, and outputstransmission signal 2507 of channel A.

Power amplifier 2508 of channel A receives and amplifies transmissionsignal 2507, and outputs transmission signal 2509 as radio-wave fromantenna 2510 of channel A.

Serial-parallel converter 2512 of channel B receives transmissiondigital signal 2511 of channel B and frame structure signal 2522, andoutputs parallel signal 2513 of channel B in accordance with the framestructure.

Inverse discrete Fourier transformer 2514 of channel B receives parallelsignal 2513, and outputs signal 2515 undergone the inverse discreteFourier transformation of channel B.

Radio unit 2516 of channel B receives signal 2515, and outputstransmission signal 2517 of channel B.

Power amplifier 2518 of channel B receives and amplifies transmissionsignal 2517, and outputs transmission signal 2519 as radio-wave fromantenna 2520 of channel B.

FIG. 26 shows a structure of the reception apparatus in accordance withthis embodiment, and radio unit 2603 receives signal 2602 received byantenna 2601, then outputs a reception quadrature baseband signal 2604.

Fourier transformer 2605 receives quadrature baseband signal 2604, andoutputs parallel signal 2606.

Transmission path variation estimation unit 2607 of channel A receivesparallel signal 2606, and outputs transmission path variation parallelsignal 2608 of channel A.

Transmission path variation estimation unit 2609 of channel B receivesparallel signal 2606, and outputs transmission path variation parallelsignal 2610 of channel B.

Radio unit 2613 receives signal 2612 received by antenna 2611, andoutputs reception quadrature baseband signal 2614.

Fourier transformer 2615 receives signal 2614, and outputs parallelsignal 2616.

Transmission path variation estimation unit 2617 of channel A receivesparallel signal 2616, and outputs transmission path variation parallelsignal 2618 of channel A.

Transmission path variation estimation unit 2619 of channel B receivesparallel signal 2616, and outputs transmission path variation parallelsignal 2620 of channel B.

Signal processor 2621 receives parallel signals 2606, 2616, transmissionpath variation parallel signals 2608, 2618 of channel A, andtransmission path variation parallel signals 2610, 2620 of channel B,then demultiplexes the signals of channel A from those of channel B, andoutputs parallel signal 2622 of channel A as well as parallel signal2623 of channel B.

Demodulator 2624 of channel A receives parallel signal 2622 of channelA, and outputs reception digital signal 2625 of channel A.

Demodulator 2626 of channel B receives parallel signal 2623 of channelB, and outputs reception digital signal 2627 of channel B.

FIG. 27 shows a transmission path variation of a carrier along a timeaxis. Specifically, relations between frame structure 2720 of carrier 1of channel A, transmission path variation 2721 of carrier 1 of channelA, frame structure 2730 of carrier 1 of channel B, transmission pathvariation 2731 of carrier 1 of channel B, and reception base-band signal2732 of carrier 1.

Frame structure 2720 includes symbol 2701 of a carrier of channel A attime 0, symbol 2702 of a carrier of channel A at time 1, symbol 2703 ofa carrier of channel A at time 2, symbol 2704 of a carrier of channel Aat time 3, symbol 2705 of a carrier of channel A at time 4, symbol 2706of a carrier of channel A at time 5. Frame structure 2730 includessymbol 2707 of a carrier of channel B at time 0, symbol 2708 of acarrier of channel B at time 1, symbol 2709 of a carrier of channel B attime 2, symbol 2710 of a carrier of channel B at time 3, symbol 2711 ofa carrier of channel B at time 4, symbol 2712 of a carrier of channel Bat time 5.

FIG. 28 shows a structure of transmission path variation estimationunits and a signal processor of carrier 1.

Estimation unit 2803 of carrier 1 of channel A receives in-phasecomponent 2801 and quadrature-phase component 2802 of carrier 1 of theparallel signal, and outputs transmission path variation estimationsignal 2804 of carrier 1 of channel A.

Estimation unit 2805 of carrier 1 of channel B receives in-phasecomponent 2801 and quadrature-phase component 2802 of carrier 1 of theparallel signal, and outputs transmission path variation estimationsignal 2806 of carrier 1 of channel B.

Estimation unit 2809 of carrier 1 of channel A receives in-phasecomponent 2807 and quadrature-phase component 2808 of carrier 1 of theparallel signal, and outputs transmission path variation estimationsignal 2810 of carrier 1 of channel A.

Estimation unit 2811 of carrier 1 of channel B receives in-phasecomponent 2807 and quadrature-phase component 2808 of carrier 1 of theparallel signal, and outputs transmission path variation estimationsignal 2812 of carrier 1 of channel B.

Signal processor 2813 of carrier 1 receives the following signals:

-   -   in-phase component 2801 and quadrature-phase component 2802 of        carrier 1 of the parallel signal;    -   transmission path variation estimation signal 2804 of carrier 1        of channel A;    -   transmission path variation estimation signal 2806 of carrier 1        of channel B;    -   in-phase component 2807 and quadrature-phase component 2808 of        carrier 1 of the parallel signal;    -   transmission path variation estimation signal 2810 of carrier 1        of channel A; and    -   transmission path variation estimation signal 2812 of carrier 1        of channel B.

Signal processor 2813 then demultiplexes the signals of channel A fromchannel B, and outputs in-phase component 2814, quadrature-phasecomponent 2815 of carrier 1 of the parallel signal of channel A, andin-phase component 2816, quadrature-phase component 2817 of carrier 1 ofthe parallel signal of channel B.

An operation of the transmission apparatus is demonstrated hereinafterwith reference to FIGS. 4, 24 and 25. In FIG. 24, the signal point ofpilot symbol 2401 corresponds to signal point 402 shown in FIG. 4. Thesignal point of symbol of (I, Q)=(0, 0) corresponds to signal point 403shown in FIG. 4.

In FIG. 25, frame structure signal generator 2521 outputs theinformation about the frame structure shown in FIG. 24 as framestructure signal 2522. Serial-parallel converter 2502 of channel Areceives transmission digital signal 2501 of channel A, frame structuresignal 2522, then outputs parallel signal 2503 of channel A inaccordance with the frame structure shown in FIG. 24. In a similar wayto converter 2502, serial-parallel converter 2512 of channel B receivestransmission digital signal 2511 of channel B, frame structure signal2522, then outputs parallel signal 2513 of channel B in accordance withthe frame structure shown in FIG. 24.

Next, an operation of the reception apparatus is demonstrated, inparticular, operations of transmission path variation estimation units2607, 2617 of channel A, estimation units 2609, 2619 of channel B, andsignal processor 2621 are demonstrated with reference to FIGS. 26, 27and 28 using carrier 1 shown in FIG. 24 as an example.

FIG. 28 shows a structure where only the functions of carrier 1 areextracted from estimation units 2607, 2617 of channel A, estimationunits 2609, 2619 of channel B, and signal processor 2621 shown in FIG.26.

In FIG. 28, in-phase component 2801 and quadrature-phase component 2802of carrier 1 of the parallel signal correspond to the component ofcarrier 1 of parallel signal 2606 shown in FIG. 26. A structure oftransmission path variation estimation unit 2803 of carrier 1 of channelA shows the function of carrier 1 in estimation unit 2607 shown in FIG.26. Estimation signal 2804 of channel A is a component of carrier 1 ofparallel signal 2608 shown in FIG. 26. A structure of transmission pathvariation estimation unit 2805 of carrier 1 of channel B shows thefunction of carrier 1 in estimation unit 2609 shown in FIG. 26.Estimation signal 2806 of channel B is a component of carrier 1 ofparallel signal 2610 shown in FIG. 26.

In-phase component 2807 and quadrature-phase component 2808 of carrier 1of the parallel signal correspond to the component of carrier 1 ofparallel signal 2616 shown in FIG. 26. A structure of transmission pathvariation estimation unit 2809 of carrier 1 of channel A shows thefunction of carrier 1 in estimation unit 2617 shown in FIG. 26.Estimation signal 2810 of channel A is a component of carrier 1 ofparallel signal 2618 in FIG. 26. A structure of transmission pathvariation estimation unit 2811 of carrier 1 of channel B shows thefunction of carrier 1 in estimation unit 2619 shown in FIG. 26.Estimation signal 2812 of channel B is a component of carrier 1 ofparallel signal 2620 in FIG. 26.

Signal processor 2813 of carrier 1 shows the function of carrier 1 insignal processor 2621. In-phase component 2814 and quadrature-phasecomponent 2815 of carrier 1 of the parallel signal of channel Acorrespond to the component of carrier 1 of parallel signal 2622 ofchannel A shown in FIG. 26. In-phase component 2816 and quadrature-phasecomponent 2817 of carrier 1 of the parallel signal of channel Bcorrespond to the component of carrier 1 of parallel signal 2623 ofchannel B shown in FIG. 26.

Next, operations of transmission path variation estimation units 2803,2809 of carrier 1 of channel A, and estimation units 2805, 2811 ofcarrier 1 of channel B shown in FIG. 28 are demonstrated using units2803 and 2805 as examples.

In FIG. 27, assume that a reception base-band signal of carrier 1 attime 0 through time 5, i.e., in-phase component 2807 andquadrature-phase component 2808 of carrier 1 in the parallel signal, are(I0, Q0), (I1, Q1), (I2, Q2), (I3, Q3), (I4, Q4), and (I5, Q5).

Assume that the transmission path variation of carrier 1 of channel A attime 0 through time 5, i.e., transmission variation estimation signal2804 of carrier 1 of channel A, are (Ia0, Qa0), (Ia1, Qa1), (Ia2, Qa2),(Ia3, Qa3), (Ia4, Qa4), and (Ia5, Qa5).

Assume that the transmission path variation of channel B of carrier 1 attime 0 through time 5, i.e., transmission variation estimation signal2806 of channel B of carrier 1, are (Ib0, Qb0), (Ib1, Qb1), (Ib2, Qb2),(Ib3, Qb3), (Ib4, Qb4), and (Ib5, Qb5).

In the foregoing case, since (I0, Q0) has only a pilot component ofchannel B of carrier 1, (Ib0, Qb0)=(I0, Q0). Similarly, since (I1, Q1)has only a pilot component of channel A of carrier 1, (Ia1, Qa1)=(I1,Q1). For instance, (Ia0, Qa0)=(Ia1, Qa1)=(Ia2, Qa2)=(Ia3, Qa3)=(Ia4,Qa4)=(Ia5, Qa5), and (Ib0, Qb0)=(Ib1, Qb1)=(Ib2, Qb2)=(Ib3, Qb3)=(Ib4,Qb4)=(Ib5, Qb5) will find transmission path variation estimation signals2804 and 2806 of channels A and B respectively of carrier 1.

A similar operation to what is discussed above will find transmissionpath variation estimation signals 2810 and 2812 of channels A and Brespectively of carrier 1.

Signal processor 2813 of carrier 1 receives the following signals:

-   -   variation estimation signals 2804, 2810 of channel A;    -   variation estimation signals 2806, 2812 of channel B;    -   in-phase component 2801, quadrature-phase component 2802 of the        parallel signal; and    -   in-phase component 2807, quadrature-phase component 2808 of the        parallel signal.

Then processor 2813 carries out matrix calculations for demultiplexingthe signals of channel A from channel B, and outputs the followingsignals:

-   -   in-phase component 2814 and quadrature-phase component 2815 of        carrier 1 of the parallel signal of channel A; and    -   in-phase component 2816 and quadrature-phase component 2817 of        carrier 1 of the parallel signal of channel B.

As a result, modulation signals of channel A and channel B can bedemultiplexed from each other, and the modulation signals can bedemodulated.

The foregoing description expresses the transmission path variation in(I, Q); however, the distortion can be expressed in power and phase, sothat estimation signals 2804, 2810 of channel A and estimation signal2806, 2812 of channel B can be expressed in power and phase.

Signals of channel A and channel B of carriers 2, 3, and 4 can bedemultiplexed from each other in a similar way to what is discussedabove using the structure shown in FIG. 28.

A method of estimating a transmission path of carrier 2 is demonstratedhereinafter. The reception apparatus of this embodiment can estimate afluctuation of the transmission path from a pilot symbol of carrier 2 attime 0 shown in FIG. 24. Also, the reception apparatus can estimate thefluctuation of the transmission path of carrier 2 at time 1 from thepilot symbols of carrier 1 and carrier 3 at time 1. As such, thetransmission path fluctuation of carrier 2 can be estimated by anestimated value of the transmission path fluctuation of carrier 2estimated at time 0 and time 1. As a result, the transmission pathfluctuation can be estimated with accuracy.

A method of estimating a transmission path of, e.g., carrier 2 shown inFIG. 24, is demonstrated hereinafter. The reception apparatus canestimate a fluctuation of the transmission path from a pilot symbol ofcarrier 2 at time 0 shown in FIG. 24. Also, the reception apparatus canestimate the fluctuation of the transmission path of carrier 2 at time 1from the pilot symbols of carrier 1 and carrier 3 at time 1. As such,the transmission path fluctuation of carrier 2 can be estimated by anestimated value of the transmission path fluctuation of carrier 2estimated at time 0 and time 1. As a result, the transmission pathfluctuation can be estimated with accuracy.

The expression of “antenna” in the previous description does not alwaysmean a single antenna, but “antenna” can mean an antenna unit which isformed of a plurality of antennas.

In this embodiment, an accuracy of demultiplexing the modulation signalsbetween channel A and channel B at the reception apparatus depends on aquality of the pilot symbol received. Thus, stronger resistance of thepilot symbol to noise increases the accuracy of isolation between themodulation signals of channel A and channel B. As a result, the qualityof data received can be improved. The way to achieve this goal isdescribed hereinafter.

In FIG. 4, assume that the pilot symbol has amplitude Ap from theorigin, and QPSK has the greatest signal-point amplitude Aq from theorigin. In this status, the relation of Ap>Aq increases the resistanceto noise of the pilot symbol, so that the accuracy of demultiplexing themodulation signals of channel A from those of channel B. As a result,the quality of data received can be improved.

In this embodiment, the number of channels to be multiplexed are two;however, other numbers can be applicable to the embodiment. The framestructure is not limited to what is shown in FIG. 24. The pilot symbolis taken as an example for demultiplexing the channels; however, othersymbols as long as they are used for demodulation can be alsoapplicable. A modulation method of the data symbol is not limited toQPSK modulation, but respective channels can undergo differentmodulations.

The structure of the transmission apparatus of this embodiment is notlimited to what is shown in FIG. 25, and when the number of channelsincrease, the structure formed of elements 2501 through 2510 shown inFIG. 25 is added accordingly.

The structure of the reception apparatus of this embodiment is notlimited to what is shown in FIGS. 26, 28, and when the number ofchannels increase, the number of channel estimation units increasesaccordingly.

As discussed above, the sixth exemplary embodiment describes thetransmission method which transmits modulation signals of a plurality ofchannels to the same frequency band from a plurality of antennas. Moreparticularly, in this method, at the time when a symbol used fordemodulation is inserted in a channel having a frame structure inaccordance with OFDM method and in the symbols of other channels ofsub-carriers, both of the same phase signal and a quadrature signal inthe in-phase-quadrature plane are made to be zero signals. The sixthembodiment also describes the transmission apparatus and the receptionapparatus to be used in the foregoing transmission method. The foregoingmethod and structure allow increasing the data transmission rate, and atthe same time, the reception apparatus can demultiplex the multiplexedmodulation signals with ease.

Exemplary Embodiment 7

The seventh exemplary embodiment describes a transmission method thatswitches between a method of transmitting modulation signals of aplurality of channels to the same frequency band from a plurality ofantennas and a method of transmitting a modulation signal of one channelfrom an antenna. The embodiment also describes a transmission apparatusand a reception apparatus to be used in the foregoing transmissionmethod.

FIG. 29 shows a frame structure in accordance with the seventhembodiment, specifically, frame structure 2910 of channel A and framestructure 2920 of channel B. Frame structure 2910 includes multiplexinformation symbols 2901, 2903, and frame symbol groups 2902, 2904 offrame A. Structure 2920 includes frame symbol group 2905 of channel B.

In this case, multiplex information symbol 2901 includes the informationthat indicates that the frame symbol groups of channel A and channel Bare transmitted simultaneously. Symbol group 2902 of channel A andsymbol group 2905 of channel B are thus transmitted simultaneously.

Multiplex information symbol 2903 includes the information whichindicates that only the frame symbol group of channel A is transmitted,so that only frame symbol group 2904 of channel A is transmitted.

FIG. 30 shows a frame structure in accordance with the seventhembodiment, specifically, frame structure 3010 of channel A and framestructure 3020 of channel B. Structure 3010 includes multiplexinformation symbol 3001 and information symbol 3002.

In this case, the multiplex information symbol at time 0 includes theinformation which indicates that the information symbol of channel A andthat of channel B are transmitted simultaneously at time 1 through time5. Those symbols are thus transmitted simultaneously at time 1 throughtime 5.

The multiplex information symbol at time 6 includes the informationwhich indicates that only the information of channel A is transmitted attime 7 through time 11.

FIG. 31 shows a structure of, e.g., a transmission apparatus at a basestation, and the apparatus comprises channel A transmitter 3120, channelB transmitter 3130, and frame structure signal generator 3118.Transmitter 3120 comprises modulation signal generator 3102, radio unit3105, power amplifier 3107, and antenna 3109. Transmitter 3130 comprisesmodulation signal generator 3102, radio unit 3111, power amplifier 3113,and antenna 3115.

Modulation signal generator 3102 receives transmission digital signal3101, frame structure signal 3119, and outputs modulation signal 3103 ofchannel A and modulation signal 3110 of channel B in accordance with theframe structure.

Radio unit 3105 of channel A receives modulation signal 3103 of channelA, and outputs transmission signal 3106 of channel A.

Power amplifier 3107 of channel A receives transmission signal 3106 ofchannel A, then amplifies it, and outputs amplified transmission signal3108 from antenna 3109 as radio wave.

Radio unit 3111 of channel B receives modulation signal 3110 of channelB, and outputs transmission signal 3112 of channel B.

Power amplifier 3113 of channel B receives transmission signal 3112 ofchannel B, then amplifies it, and outputs amplified transmission signal3114 from antenna 3115 as radio wave.

Frame structure signal generator 3118 receives radio-wave propagationenvironmental information 3116, transmission data amount information3117, then outputs frame structure signal 3119.

FIG. 32 shows a structure of, e.g., a reception apparatus at a terminalin accordance with this embodiment. Radio unit 3203 receives signal 3202received by antenna 3201, and outputs reception quadrature basebandsignal 3204.

Multiplex information symbol demodulator 3205 receives base-band signal3204, and multiplex information data 3206.

Transmission path variation estimation unit 3207 of channel A receivesbase-band signal 3204, and outputs variation estimation signal 3208.Transmission path variation estimation unit 3209 of channel B receivesbase-band signal 3204, and outputs variation estimation signal 3210.

Radio unit 3213 receives signal 3212 received by antenna 3211, andoutputs reception quadrature baseband signal 3214. Transmission pathvariation estimation unit 3215 of channel A receives base-band signal3214, and outputs variation estimation signal 3216. Transmission pathvariation estimation unit 3217 of channel B receives base-band signal3214, and outputs variation estimation signal 3218.

Signal processor 3219 receives the following signals:

-   -   transmission path variation estimation signals 3208, 3216 of        channel A;    -   transmission path variation estimation signals 3210, 3218 of        channel B;    -   reception quadrature baseband signals 3204, 3214; and    -   multiplex information data 3206.

Signal processor 3219 then outputs signal 3220 of channel A and signal3221 of channel B based on multiplex information data 3206.

Demodulator 3222 receives signals 3220, 3221, data 3206, and based ondata 3206, outputs reception digital signal 3223.

Radio-wave propagation environment estimation unit 3224 receivesbase-band signal 3204, 3214, then estimates the radio-wave propagationenvironment, e.g., a received signal strength intensity or a spatialcorrelation of the radio-wave propagation environment, and outputsradio-wave propagation environment estimation signal 3225.

The transmission apparatus of, e.g., a base station, in accordance withthe embodiment with reference to FIGS. 29, 31, and 32.

The reception apparatus shown in FIG. 32 includes radio-wave propagationenvironment estimation unit 3224 which receives reception quadraturebaseband signal 3204, 3214. Estimation unit 3224 then estimates theradio-wave propagation environment, e.g., a received signal strengthintensity or a spatial correlation of the radio-wave propagationenvironment, and outputs radio wave propagation environment estimationsignal 3225. The information of signal 3225 is transmitted as data froma transmitter of the terminal, and the base station receives anddemodulates it for obtaining the information corresponding to signal3225. This information corresponds to radio-wave propagationenvironmental information 3116 shown in FIG. 31.

Frame structure signal generator 3118 receives information 3116,transmission data amount information 3117, and outputs frame structuresignal 3119 that includes, e.g., the following information as shown inFIG. 29:

Multiplex information symbol 2901 indicates that the frame symbol groupsof channels A and B are simultaneously transmitted;

Frame symbol group 2902 of channel A and frame symbol group 2905 ofchannel B indicate that both of them are transmitted simultaneously;

Multiplex information symbol 2903 of channel A indicates that only theframe symbol groups of channel A are transmitted; and

Multiplex information symbol 2904 of channel A indicates that only theframe symbol groups of channel A are transmitted.

Modulation signal generator 3102 shown in FIG. 31 receives transmissiondigital signal 3101, frame structure signal 3119, and outputs modulationsignal 3103 of channel A and modulation signal 3110 of channel B.

The reception apparatus of the terminal in accordance with the seventhembodiment is described with reference to FIG. 29 and FIG. 32. Multiplexinformation symbol decoder 3205 receives reception quadrature basebandsignal 3204, then demodulates the multiplex information symbol shown inFIG. 29. When decoder 3205 decodes, e.g., multiplex information symbol2901, decoder 3205 outputs the following information as multiplexinformation data 3206: The information indicating that the frame symbolgroups of channels A and B are transmitted simultaneously. When decoder3205 decodes, e.g., multiplex information symbol 2903, decoder 3205outputs the following information as multiplex information data 3206:the information indicating that the frame symbol group of only channel Ais transmitted.

Signal processor 3219 receives the following signals:

-   -   transmission path variation estimation signals 3208, 3216 of        channel A;    -   transmission path variation estimation signals 3210, 3218 of        channel B;    -   reception quadrature baseband signals 3204, 3214; and    -   multiplex information data 3206.

When data 3206 indicates that the frame symbol groups of channels A andB are transmitted simultaneously, processor 3219 carries out inversematrix calculations from estimation signals 3208, 3216 of channel A,estimation signals 3210, 3218 of channel B, base-band signals 3204,3214. Then processor 3219 demultiplexes the signals of channel A fromthose of channel B, and outputs signal 3220 of channel A and signal 3221of channel B. When multiplex information data 3206 indicates that theframe symbol group of only channel A is transmitted, processor 3219outputs only signal 3220 of channel A.

Demodulator 3222 receives signal 3220 of channel A, signal 3221 ofchannel B, and multiplex information data 3206. When data 3206 indicatesthat the frame symbol groups of channels A and B are simultaneouslytransmitted, decoder 3222 decodes signals 3220, 3221. When data 3206indicates that the frame symbol group of only channel A is transmitted,demodulator 3222 demodulates signal 3220 of channel A. Then demodulator3222 outputs reception digital signal 3223.

In the case of orthogonal frequency multiplexing (OFDM) system, asimilar way to what is discussed above is applicable. The transmitter ofthe base station, for instance, in accordance with the seventhembodiment is demonstrated hereinafter with reference to FIGS. 30, 31,32.

The reception apparatus shown in FIG. 32 includes radio-wave propagationenvironment estimation unit 3224 which receives reception quadraturebaseband signal 3204, 3214. Estimation unit 3224 then estimates theradio-wave propagation environment, e.g., received signal strengthintensity or spatial correlation of the radio-wave propagationenvironment, and outputs radio wave propagation environment estimationsignal 3225. The information of signal 3225 is transmitted as data froma transmitter of the terminal, and the base station receives anddemodulates it for obtaining the information corresponding to signal3225. This information corresponds to radio-wave propagationenvironmental information 3116 shown in FIG. 31.

Frame structure signal generator 3118 receives information 3116,transmission data amount information 3117, and outputs frame structuresignal 3119 that includes, e.g., the following information as shown inFIG. 30:

-   -   multiplex information symbol at time 0 indicating that the        information symbols of channels A and B are simultaneously        transmitted at time 1-time 5, and showing the frame structure        where both of information symbols of channel A and channel B are        transmitted simultaneously at time 1-time 5;    -   multiplex information symbol at time 6 indicating that only the        information of channel A is transmitted at time 7-time 11, and        showing the frame structure where the information of only        channel A is transmitted at time 7-time 11.

Generator 3118 outputs the foregoing information as frame structuresignal 3119.

Modulation signal generator 3102 receives transmission digital signal3101, frame structure signal 3119, and outputs modulation signal 3103 ofchannel A and modulation signal 3110 of channel B in accordance with theframe structure.

Next, a reception apparatus of a terminal in accordance with the seventhembodiment is described with reference to FIG. 30 and FIG. 32.

Multiplex information symbol demodulator 3205 receives base-band signal3204, and demodulates the multiplex information symbol shown in FIG. 30.When, for instance, demodulator 3205 demodulates the multiplexinformation symbol at time 0, demodulator 3205 outputs the informationindicating that the frame symbol groups of channels A and B aretransmitted simultaneously. When demodulator 3205 demodulates the symbolat time 6, demodulator 3205 outputs the information indicating that theframe symbol group of only channel A is transmitted. As such, theinformation of either one of the foregoing cases is output as multiplexinformation data 3206.

Signal processor 3219 receives the following signals:

-   -   transmission path variation estimation signals 3208, 3216 of        channel A;    -   transmission path variation estimation signals 3210, 3218 of        channel B;    -   reception quadrature baseband signals 3204, 3214; and    -   multiplex information data 3206.

When data 3206 indicates that the frame symbol groups of channels A andB are transmitted simultaneously, processor 3219 carries out inversematrix calculations from estimation signals 3208, 3216 of channel A,estimation signals 3210, 3218 of channel B, base-band signals 3204,3214. Then processor 3219 demultiplexes the signals of channel A fromthose of channel B, and outputs signal 3220 of channel A and signal 3221of channel B. When multiplex information data 3206 indicates that theframe symbol group of only channel A is transmitted, processor 3219outputs only signal 3220 of channel A.

Demodulator 3222 receives signal 3220 of channel A, signal 32210 ofchannel B, and multiplex information data 3206. When data 3206 indicatesthat the frame symbol groups of channels A and B are simultaneouslytransmitted, decoder 3222 decodes signals 3220, 3221. When data 3206indicates that the frame symbol group of only channel A is transmitted,demodulator 3222 demodulates signal 3220 of channel A. Then demodulator3222 outputs reception digital signal 3223.

In this embodiment, the number of channels to be multiplexed are two;however, other numbers can be applicable to this embodiment. The framestructure is not limited to what is shown in FIG. 29 or FIG. 30.

The structure of the transmission apparatus of this embodiment is notlimited to what is shown in FIG. 31, and when the number of channelsincrease, the structure formed of elements 3103 through 3109 shown inFIG. 31 is added accordingly. The structure of the reception apparatusof this embodiment is not limited to what is shown in FIG. 32.

The expression of “antenna” in the previous description does not alwaysmean a single antenna, but “antenna” can mean an antenna unit which isformed of a plurality of antennas.

The seventh exemplary embodiment as discussed above describes thetransmission method that switches between the method of transmittingmodulation signals of a plurality of channels to the same frequency bandfrom a plurality of antennas and the method of transmitting a modulationsignal of one channel from an antenna. The embodiment also describes thetransmission apparatus and the reception apparatus used in the foregoingtransmission method. Multiplexing the transmission signals of aplurality of channels to the same frequency band allows the method andthe apparatuses to increase the data transmission rate, and allows thereception apparatus to demultiplex the multiplexed modulation signalsreceived with ease.

Exemplary Embodiment 8

The eighth exemplary embodiment describes a transmission method ofmultiplexing modulation signals of a plurality of channels to the samefrequency band, more particularly, a method of transmitting asynchronous symbol for the foregoing transmission method. Thisembodiment also describes a transmission apparatus as well as areception apparatus to be used in the foregoing transmission method.

FIG. 2 shows a structure of the transmission apparatus in accordancewith the eighth embodiment.

FIG. 4 shows a placement of signal points in the in-phase-quadratureplane in accordance with this embodiment.

FIG. 33 shows a frame structure along a time-axis in accordance withthis embodiment, and to be more specific, it shows frame structure 3310of channel A and frame structure 3320 of channel B. Frame structures3310, 3320 include synchronous symbols 3301, 3305, guard symbols 3302,3304, and data symbols 3303, 3306.

FIG. 34 shows a frame structure along a time axis in accordance withthis embodiment, specifically, frame structure 3410 of channel A andframe structure 3420 of channel B. Structures 3410, 3420 includesynchronous symbols 3401, data symbols 3402, 3404, and guard symbol3403.

FIG. 35 shows a structure of modulation signal generators 202, 212, andthe elements operating in a similar way to those in FIG. 3 have the samereference marks. Synchronous symbol modulation signal generator 3501receives frame structure signal 311, and outputs in-phase component 3502and quadrature-phase component 3503 of the transmission quadraturebaseband signal of the synchronous symbol when frame structure signal311 indicates the synchronous symbol.

In-phase component switcher 312 receives the following signals:

-   -   in-phase component 303 of a data symbol transmission quadrature        baseband signal;    -   in-phase component 3502 of the synchronous symbol transmission        quadrature baseband signal;    -   in-phase component 309 of a guard symbol transmission quadrature        baseband signal, and frame structure signal 311,    -   then switcher 312 selects the in-phase component of transmission        quadrature baseband signal corresponding to a symbol indicated        by frame structure signal 311, and outputs the selected one as        in-phase component 313 of the selected transmission quadrature        baseband signal.

Quadrature-phase component switcher 314 receives the following signals:

-   -   quadrature-phase component 304 of a data symbol transmission        quadrature baseband signal;    -   quadrature-phase component 3503 of the synchronous symbol        transmission quadrature baseband signal;    -   quadrature-phase component 310 of a guard symbol transmission        quadrature baseband signal, and frame structure signal 311,    -   then selects a quadrature-phase component of a transmission        quadrature baseband signal corresponding to a symbol indicated        by frame structure signal 311, and outputs the selected one as        quadrature-phase component 315 of the selected transmission        quadrature baseband signal.

FIG. 36 shows a structure of modulation signal generators 202, 212 shownin FIG. 2. Guard symbol or synchronous symbol transmission signalgenerator 3601 receives frame structure signal 311, and outputs in-phasecomponent 3602, quadrature-phase component 3603 of the transmissionquadrature baseband signal of the guard symbol or the synchronoussymbol.

FIG. 37 shows a structure of the reception apparatus in accordance withthe eighth embodiment, and its radio unit 3703 receives signal 3702received by antenna 3701, then outputs reception quadrature basebandsignal 3704.

Transmission path variation estimation unit 3705 receives base-bandsignal 3704 and timing signal 3719, then outputs transmission pathvariation estimation signal 3706.

Radio unit 3708 receives signal 3707 received by antenna 3706, thenoutputs reception quadrature baseband signal 3709.

Transmission path variation estimation unit 3710 receives base-bandsignal 3709 and timing signal 3719, then outputs transmission pathvariation estimation signal 3711.

Radio unit 3714 receives signal 3713 received by antenna 3712, thenoutputs reception quadrature baseband signal 3715.

Transmission path variation estimation unit 3716 receives base-bandsignal 3715 and timing signal 3719, then outputs transmission pathvariation estimation signal 3717.

Synchronizing unit 3718 receives base-band signal 3715, and searches fora synchronous symbol transmitted by the transmission apparatus tosynchronize with the transmission apparatus, then outputs timing signal3719.

Signal isolator 3720 receives the following signals:

-   -   reception quadrature baseband signals 3704, 3709, 3715;    -   transmission path variation estimation signals 3706, 3711, 3717;        and    -   timing signal 3719.

Signal isolator 3720 then outputs reception quadrature baseband signal3721 of channel A and quadrature baseband signal 3722 of channel B.

Demodulator 3723 receives signal 3721 of channel A, and outputsreception digital signal 3724. Demodulator 3725 receives signal 3722 ofchannel B, and outputs reception digital signal 3725.

FIG. 38 shows a structure of the reception apparatus in accordance withthe eighth embodiment, and the elements operating in a similar way tothose in FIG. 37 have the same reference marks.

Synchronizing unit 3801 receives reception quadrature baseband signal3704, and searches for a synchronous symbol transmitted by thetransmission apparatus to synchronize with the transmission apparatus,then outputs timing signal 3802.

Transmission path variation estimation unit 3705 receives base-bandsignal 3704 and timing signal 3802, then outputs transmission pathvariation estimation signal 3706.

Synchronizing unit 3803 receives reception quadrature baseband signal3709, and searches for a synchronous symbol transmitted by thetransmission apparatus to synchronize with the transmission apparatus,then outputs timing signal 3804.

Transmission path variation estimation unit 3710 receives receptionquadrature baseband signal 3709 and timing signal 3804, then outputstransmission path variation estimation signal 3711.

Synchronizing unit 3805 receives reception quadrature baseband signal3715, and searches for a synchronous symbol transmitted by thetransmission apparatus to synchronize with the transmission apparatus,then outputs timing signal 3806.

Transmission path variation estimation unit 3716 receives receptionquadrature baseband signal 3715 and timing signal 3806, then outputstransmission path variation estimation signal 3717.

FIG. 39 shows a structure of the reception apparatus in accordance withthe eighth embodiment, and the elements operating in a similar way tothose in FIG. 37 have the same reference marks.

Received signal strength intensity estimation unit 3901 receives signal3702, then estimates the received signal strength intensity, and outputsreceived signal strength intensity estimation signal 3902.

Received signal strength intensity estimation unit 3903 receives signal3707, then estimates the received signal strength intensity, and outputsreceived signal strength intensity estimation signal 3904.

FIG. 40 shows a structure of the reception apparatus in accordance withthe eighth embodiment, and the elements operating in a similar way tothose in FIG. 37 or FIG. 39 have the same reference marks.

Signal selection unit 4001 receives the following signals:

-   -   received signal strength intensity estimation signals 3902,        3904, 3906; and    -   reception quadrature baseband signal 3704, 3709, 3715,    -   then unit 4001 selects, e.g., the reception quadrature baseband        signal supplied from the antenna that receives the signal having        the best electric field among the received signal strength        intensity estimation signals, and outputs it as reception        quadrature baseband signal 4002.

Synchronizing unit 4003 receives reception quadrature baseband signal4002 selected, and searches for a synchronous symbol transmitted by thetransmission apparatus to synchronize with the transmission apparatus,then outputs timing signal 4004.

FIG. 41 shows a structure of the reception apparatus in accordance withthe eighth embodiment, and the elements operating in a similar way tothose in FIG. 39 or FIG. 40 have the same reference marks.

An operation of the transmission apparatus is demonstrated hereinafterwith reference to FIGS. 2, 4, 33, 34, 35 and 36.

Frame structure signal generator 209 outputs the information of theframe structure shown in FIG. 33 or FIG. 34 as frame structure signal210. Modulation signal generator 202 of channel A receives framestructure signal 210 and transmission digital signal 201 of channel A,then outputs modulation signal 203 of channel A in accordance with theframe structure. Modulation signal generator 212 of channel B receivesframe structure signal 210 and transmission digital signal 211 ofchannel B, then outputs modulation signal 213 of channel B in accordancewith the frame structure.

Next, an operation of modulation signal generators 202 and 212 inaccordance with the frame structure shown in FIG. 33 is described withreference to FIG. 35 using a transmitter of channel A as an example.

Data symbol modulation signal generator 302 receives transmissiondigital signal 301, i.e., transmission digital signal 201 of channel Ain FIG. 2, and frame structure signal 311, i.e., frame structure signal210 in FIG. 2. When frame structure signal 311 indicates a data symbol,generator 302 outputs in-phase component 303 and quadrature-phasecomponent 304 of a transmission quadrature baseband signal of the datasymbol.

Synchronous symbol modulation signal generator 3501 receives framestructure signal 311. When frame structure signal 311 indicates thesynchronous symbol, generator 3501 outputs in-phase component 3502 andquadrature-phase component 3503 of the transmission quadrature basebandsignal of the synchronous symbol.

Guard symbol modulation signal generator 308 receives frame structuresignal 311. When signal 311 indicates a guard symbol, generator 308outputs in-phase component 309 and quadrature-phase component 310 of atransmission quadrature baseband signal of the guard symbol.

FIG. 4 shows the signal-point placement of the respective symbols in anin-phase-quadrature plane of the foregoing operation. Points 401 in FIG.4 indicate the signal-points of in-phase component 303 andquadrature-phase component 304 of the transmission quadrature basebandsignal of the data symbol. Points 402 indicate the signal-points ofin-phase component 3502 and quadrature-phase component 3503 of thetransmission quadrature baseband signal of the synchronous symbol. Point403 indicates the signal-points of in-phase component 309 andquadrature-phase component 310 of the transmission quadrature basebandsignal of the guard symbol.

In-phase component switcher 312 receives the following signals:

-   -   in-phase component 303 of data symbol transmission quadrature        baseband signal;    -   in-phase component 3502 of synchronous symbol transmission        quadrature baseband signal;    -   in-phase component 309 of guard symbol transmission quadrature        baseband signal; and    -   frame structure signal 311.

Switcher 312 then selects an in-phase component of a transmissionquadrature baseband signal corresponding to the symbol indicated byframe structure signal 311, and outputs the selected one as in-phasecomponent 313 of the selected transmission quadrature baseband signal.

Quadrature-phase component switcher 314 receives the following signals:

-   -   quadrature-phase component 304 of data symbol transmission        quadrature baseband signal;    -   quadrature-phase component 3503 of synchronous symbol        transmission quadrature baseband signal;    -   quadrature-phase component 310 of guard symbol transmission        quadrature baseband signal; and    -   frame structure signal 311.

Switcher 314 then selects a quadrature-phase component of a transmissionquadrature baseband signal corresponding to the symbol indicated byframe structure signal 311, and outputs the selected one asquadrature-phase component 315 of the selected transmission quadraturebaseband signal.

Orthogonal modulator 316 receives in-phase component 313 andquadrature-phase component 315 discussed above, then provides thosecomponents with an orthogonal modulation, and outputs modulation signal317, i.e., signal 203 shown in FIG. 2.

An operation of modulation signal generators 202, 212 at frame structure34 is demonstrated with reference to FIG. 36.

An operation of generator 202 is demonstrated hereinafter. Data symbolmodulation signal generator 302 receives transmission digital signal301, i.e., transmission digital signal 201 of channel A in FIG. 2, andframe structure signal 311, i.e., frame structure signal 210 in FIG. 2.When frame structure signal 311 indicates a data symbol, generator 302outputs in-phase component 303 and quadrature-phase component 304 of atransmission quadrature baseband signal of the data symbol.

Synchronous symbol modulation signal generator 3601 receives framestructure signal 311, and outputs in-phase component 3602 andquadrature-phase component 3603 of the transmission quadrature basebandsignal of the synchronous symbol when frame structure signal 311indicates the synchronous symbol.

FIG. 4 shows the signal-point placement of the respective symbols in anin-phase-quadrature plane of the foregoing operation. Points 401 in FIG.4 indicate the signal-points of in-phase component 303 andquadrature-phase component 304 of the transmission quadrature basebandsignal of the data symbol. Points 402 indicate the signal-points ofin-phase component 3602 and quadrature-phase component 3603 of thetransmission quadrature baseband signal of the synchronous symbol.

In-phase component switcher 312 receives the following signals:

-   -   in-phase component 303 of data symbol transmission quadrature        baseband signal;    -   in-phase component 3602 of synchronous symbol transmission        quadrature baseband signal, and frame structure signal 311.

Switcher 312 then selects an in-phase component of a transmissionquadrature baseband signal corresponding to the symbol indicated byframe structure signal 311, and outputs the selected one as in-phasecomponent 313 of the selected transmission quadrature baseband signal.

Quadrature-phase component switcher 314 receives the following signals:

-   -   quadrature-phase component 304 of data symbol transmission        quadrature baseband signal;    -   quadrature-phase component 3603 of synchronous symbol        transmission quadrature baseband signal, and frame structure        signal 311.

Switcher 314 then selects a quadrature-phase component of a transmissionquadrature baseband signal corresponding to the symbol indicated byframe structure signal 311, and outputs the selected one asquadrature-phase component 315 of the selected transmission quadraturebaseband signal.

Orthogonal modulator 316 receives in-phase component 313 andquadrature-phase component 315 discussed above, then provides thosecomponents with an orthogonal modulation, and outputs modulation signal317, i.e., signal 203 shown in FIG. 2.

An operation of generator 212 is demonstrated hereinafter. Data symbolmodulation signal generator 302 receives transmission digital signal301, i.e., transmission digital signal 211 of channel B in FIG. 2, andframe structure signal 210, i.e., frame structure signal 311 in FIG. 36.When frame structure signal 311 indicates a data symbol, generator 302outputs in-phase component 303 and quadrature-phase component 304 of atransmission quadrature baseband signal of the data symbol.

Guard symbol modulation signal generator 3601 receives frame structuresignal 311. When signal 311 indicates a guard symbol, generator 3601outputs in-phase component 3602 and quadrature-phase component 3603 of atransmission quadrature baseband signal of the guard symbol.

FIG. 4 shows the signal-point placement of the respective symbols in anin-phase-quadrature plane of the foregoing operation. Points 401 in FIG.4 indicate the signal-points of in-phase component 303 andquadrature-phase component 304 of the transmission quadrature basebandsignal of the data symbol. Points 403 indicate the signal-points ofin-phase component 3602 and quadrature-phase component 3603 of thetransmission quadrature baseband signal of the guard symbol.

In-phase component switcher 312 receives the following signals:

-   -   in-phase component 303 of the data symbol transmission        quadrature baseband signal;    -   in-phase component 3602 of the guard symbol transmission        quadrature baseband signal, and frame structure signal 311.

Switcher 312 then selects an in-phase component of a transmissionquadrature baseband signal corresponding to the symbol indicated byframe structure signal 311, and outputs the selected one as in-phasecomponent 313 of the selected transmission quadrature baseband signal.

Quadrature-phase component switcher 314 receives the following signals:

-   -   quadrature-phase components 304 of a data symbol transmission        quadrature baseband signal;    -   quadrature-phase component 3603 of the guard symbol transmission        quadrature baseband signal, and frame structure signal 311,    -   then selects a quadrature-phase component of a transmission        quadrature baseband signal corresponding to a symbol indicated        by frame structure signal 311, and outputs the selected one as        quadrature-phase component 315 of the selected transmission        quadrature baseband signal.

Orthogonal modulator 316 receives in-phase component 313 andquadrature-phase component 315 selected as discussed above, thenprovides those components with an orthogonal modulation, and outputsmodulation signal 317, i.e., signal 213 shown in FIG. 2.

An operation of the reception apparatus is demonstrated hereinafter withreference to FIG. 37 through FIG. 42. First, the operation isdemonstrated with reference to FIG. 37.

Radio unit 3714 receives signal 3713 received by antenna 3712, thenoutputs reception quadrature baseband signal 3715.

Synchronizing unit 3718 receives base-band signal 3715, and detects asynchronous symbol among the signals transmitted by the transmissionapparatus, then outputs timing signal 3719 which synchronizes with thetransmission apparatus time-wise. Signal 3719 is used as a timing signalat the respective units in the reception apparatus.

Next, an operation of the reception apparatus is demonstrated withreference to FIG. 38.

Radio unit 3703 receives signal 3702 received by antenna 3701, thenoutputs reception quadrature baseband signal 3704.

Synchronizing unit 3801 receives base-band signal 3704, and detects asynchronous symbol among the signals transmitted by the transmissionapparatus, then outputs timing signal 3802 which synchronizes with thetransmission apparatus time-wise. Signal 3802 is, e.g., supplied totransmission path variation estimation unit 3705 and signal isolator3807. Signal isolator 3807 then extracts a signal from base-band signal3704 by timing to itself for signal processing.

Radio unit 3708 receives signal 3707 received by antenna 3706, thenoutputs reception quadrature baseband signal 3709.

Synchronizing unit 3803 receives base-band signal 3709, and detects asynchronous symbol among the signals transmitted by the transmissionapparatus, then outputs timing signal 3804 which synchronizes with thetransmission apparatus time-wise. Signal 3804 is, e.g., supplied totransmission path variation estimation unit 3710 and signal isolator3807. Signal isolator 3807 then extracts a signal from base-band signal3709 by timing to itself for signal processing.

Radio unit 3714 receives signal 3713 received by antenna 3712, thenoutputs reception quadrature baseband signal 3715.

Synchronizing unit 3805 receives base-band signal 3715, and detects asynchronous symbol among the signals transmitted by the transmissionapparatus, then outputs timing signal 3806 which synchronizes with thetransmission apparatus time-wise. Signal 3806 is, e.g., supplied totransmission path variation estimation unit 3716 and signal isolator3807. Signal isolator 3807 then extracts a signal from base-band signal3715 by timing to itself for signal processing.

Next, an operation of the reception apparatus is demonstrated withreference to FIG. 39.

Received signal strength intensity estimation unit 3901 receives signal3702 received by antenna 3701, then estimates the reception receivedsignal strength intensity, and outputs received signal strengthintensity estimation signal 3902.

In a similar way to what is discussed above, received signal strengthintensity estimation unit 3903 receives signal 3707 received by antenna3706, then estimates the reception received signal strength intensity,and outputs received signal strength intensity estimation signal 3904.Received signal strength intensity estimation unit 3905 receives signal3713 received by antenna 3712, then estimates the reception receivedsignal strength intensity, and outputs received signal strengthintensity estimation signal 3906.

Synchronizing unit 3907 receives reception quadrature baseband signal3704, and detects a synchronous symbol among the signals transmitted bythe transmission apparatus, then outputs timing signal 3908 whichsynchronizes with the transmission apparatus time-wise.

In a similar way to what is discussed above, synchronizing unit 3909receives reception quadrature baseband signal 3709, and detects asynchronous symbol among the signals transmitted by the transmissionapparatus, then outputs timing signal 3910 which synchronizes with thetransmission apparatus time-wise. Synchronizing unit 3911 receivesreception quadrature baseband signal 3715, and detects a synchronoussymbol among the signals transmitted by the transmission apparatus, thenoutputs timing signal 3912 which synchronizes with the transmissionapparatus time-wise.

Synchronous signal selection unit 3913 receives received signal strengthintensity estimation signals 3902, 3904, 3906, and timing signals 3908,3910, 3912. When the electric field of the signal received by, e.g.,antenna 3701 is the strongest among others, timing signal 3908 isselected from the foregoing estimation signals. Selection unit 3913 thenoutputs timing signal 3908 selected as timing signal 3914. As such, thetiming signal found from the reception signal that has the best electricfield is used as the timing signal of the reception apparatus.

Next, an operation of the reception apparatus is demonstrated withreference to FIG. 40.

Signal selection unit 4001 receives the following signals:

-   -   received signal strength intensity estimation signals 3902,        3904, 3906; and    -   reception quadrature baseband signals 3704, 3709, 3715,

When the electric field of the signal received by, e.g., antenna 3701 isthe strongest among others, base-band signal 3704 is selected from theforegoing base-band signals. Then unit 4001 outputs signal 3704 asreception quadrature baseband signal 4002.

Synchronizing unit 4003 receives reception quadrature baseband signal4002 selected, and searches for a synchronous symbol transmitted by thetransmission apparatus, then outputs timing signal 4004 whichsynchronizes with the transmission apparatus. As such, the timing signalfound from the reception signal that has the best electric field is usedas the timing signal of the reception apparatus.

Next, an operation of the reception apparatus is demonstrated withreference to FIG. 41. The operation shown in FIG. 41 differs from thatof FIG. 39 in finding the received signal strength intensity by using areception quadrature baseband signal.

Received signal strength intensity estimation unit 3901 receivesreception quadrature baseband signal 3704, then estimates the receptionreceived signal strength intensity, and outputs received signal strengthintensity estimation signal 3902.

In a similar way to what is discussed above, received signal strengthintensity estimation unit 3903 receives reception quadrature basebandsignal 3709, then estimates the reception received signal strengthintensity, and outputs received signal strength intensity estimationsignal 3904. Received signal strength intensity estimation unit 3905receives reception quadrature baseband signal 3715, then estimates thereception received signal strength intensity, and outputs receivedsignal strength intensity estimation signal 3906.

The operation shown in FIG. 42 differs from that of FIG. 40 in findingthe received signal strength intensity by using a reception quadraturebaseband signal.

In the foregoing discussion, the received signal strength intensity isused as an example of a parameter of the radio-wave propagationenvironment; however, this embodiment is not limited to this example,and Doppler frequency or the number of paths of multi-path can be usedas the parameter.

The foregoing discussion proves that the transmission apparatus can besynchronized with the reception apparatus time-wise.

In this embodiment, the number of channels to be multiplexed are two;however, other numbers can be applicable to the embodiment. The framestructure is not limited to what is shown in FIG. 33 or FIG. 34. Amodulation method of the data symbol is not limited to QPSK modulation,but respective channels can undergo different modulations. On the otherhand, all the channels can use the spread spectrum communication method.The spread spectrum communication method can coexist with the othermethods.

The synchronous symbols shown in FIGS. 33, 34 are used fortime-synchronizing the reception apparatus with the transmissionapparatus; however, the symbols are not limited to this usage, and theycan be used for, e.g., estimating a frequency offset between thereception apparatus and the transmission apparatus.

The structure of the transmission apparatus of this embodiment is notlimited to what is shown in FIGS. 2, 35, 36, and when the number ofchannels increases, the structure formed of elements 201 through 208shown in FIG. 31 is added accordingly.

The structure of the reception apparatus of this embodiment is notlimited to what is shown in FIG. 37 through FIG. 42; but the number ofantennas can be increased.

The expression of “antenna” in the previous description does not alwaysmean a single antenna, but “antenna” can mean an antenna unit which isformed of a plurality of antennas.

The eighth exemplary embodiment, as discussed above, describes thetransmission method of multiplexing modulation signals of a plurality ofchannels to the same frequency band, more particularly, the method oftransmitting a synchronous symbol in the foregoing transmission method.This embodiment also describes the transmission apparatus and thereception apparatus to be used in the foregoing transmission method. Themethod and the apparatuses can increase the transmission rate of data,and synchronize the transmission apparatus with the reception apparatustime-wise.

Exemplary Embodiment 9

The ninth exemplary embodiment describes a transmission method oftransmitting modulation signals of a plurality of channels to the samefrequency band from a plurality of antennas, more particularly, a methodof transmitting a synchronous symbol in the spread-spectrum transmissionmethod. The ninth embodiment also describes a transmission apparatus anda reception apparatus to be used in the foregoing transmission method.

FIG. 4 shows a placement of signal points in the in-phase-quadratureplane in accordance with this embodiment.

FIG. 12 shows a structure of the transmission apparatus in accordancewith the eighth embodiment.

FIG. 43 shows a frame structure along a time-axis in accordance withthis embodiment, and to be more specific, it shows frame structure 4310of spread-spectrum communication method A and frame structure 4320 ofmethod B. Frame structures 4310, 4320 include synchronous symbols 4301,4305, guard symbols 4302, 4304, and data symbols 4303, 4306.

FIG. 44 shows a frame structure along a time axis in accordance withthis embodiment, specifically, frame structure 4410 of method A andframe structure 4420 of method B. Structures 4410, 4420 includesynchronous symbols 4401, data symbols 4402, 4404, and guard symbol4403.

FIG. 45 shows a frame structure along a time axis in accordance withthis embodiment, specifically, frame structure 4510 of method A andframe structure 4520 of method B. Structures 4510, 4520 include guardsymbols 4503, 4505, 4507, data symbols 4502, 4504, 4506, 4508 andsynchronous symbol 4501.

FIG. 46 shows a structure of modulation signal generators 1202, 1210,and the elements operating in a similar way to those in FIG. 13 have thesame reference marks.

Guard symbol modulation signal generator 4601 receives frame structuresignal 1320. When signal 1320 indicates a guard symbol, generator 4601outputs in-phase component 4602 and quadrature-phase component 4603 of atransmission quadrature baseband signal of the guard symbol.

Synchronous symbol modulation signal generator 4604 receives framestructure signal 1320, and outputs in-phase component 4605 andquadrature-phase component 4606 of the transmission quadrature basebandsignal of the synchronous symbol when frame structure signal 1320indicates the synchronous symbol.

FIG. 47 shows a structure of modulation signal generators 1202, 1210shown in FIG. 12, and the elements operating in a similar way to thosein FIG. 13 have the same reference marks.

Guard symbol or synchronous symbol modulation signal generator 4701receives frame structure signal 1320, and outputs in-phase component4702, quadrature-phase component 4703 of a transmission quadraturebaseband signal of the guard symbol or the synchronous symbol.

FIG. 48 shows a structure of modulation signal generators 1202, 1210shown in FIG. 12, and the elements operating in a similar way to thosein FIG. 13 have the same reference marks.

Primary modulator 4802 receives control information 4801 and framestructure signal 1320, and outputs in-phase component 4803,quadrature-phase component 4804 of the transmission quadrature basebandsignal undergone the primary modulation.

Synchronous symbol transmission signal generator 4805 receives framestructure signal 1320, and outputs in-phase component 4806,quadrature-phase component 4807 of the transmission quadrature basebandsignal of the synchronous symbol.

Spread unit 4808 receives the following signals:

-   -   in-phase component 4803 and quadrature-phase component 4804 of        the transmission quadrature baseband signal undergone the        primary modulation;    -   in-phase component 4806, quadrature-phase component 4807 of the        synchronous symbol transmission quadrature baseband signal;    -   spread code 1317; and    -   frame structure signal 1320.

Spread unit 4808 then outputs in-phase component 4809 andquadrature-phase component 4810 of a transmission quadrature basebandsignal corresponding to frame structure signal 1320 and undergone thespread of the symbol.

FIG. 49 shows a structure of modulation signal generators 1202, 1210shown in FIG. 12, and the elements operating in a similar way to thosein FIG. 13 or FIG. 48 have the same reference marks.

Guard symbol modulation signal generator 4901 receives frame structuresignal 1320, then outputs in-phase component 4902 and quadrature-phasecomponent 4903 of a transmission quadrature baseband signal of the guardsymbol.

Spread unit 4808 receives the following signals:

-   -   in-phase component 4803 and quadrature-phase component 4804 of        the transmission quadrature baseband signal undergone the        primary modulation;    -   in-phase component 4902, quadrature-phase component 4903 of the        synchronous symbol transmission quadrature baseband signal;    -   spread code 1317; and    -   frame structure signal 1320.

Spread unit 4808 then outputs in-phase component 4809 andquadrature-phase component 4810 of a transmission quadrature basebandsignal corresponding to frame structure signal 1320 and undergone thespread of the symbol.

FIG. 37 shows a structure of a reception apparatus in accordance withthis exemplary embodiment.

FIG. 38 shows a structure of a reception apparatus in accordance withthis exemplary embodiment.

FIG. 39 shows a structure of a reception apparatus in accordance withthis exemplary embodiment.

FIG. 40 shows a structure of a reception apparatus in accordance withthis exemplary embodiment.

FIG. 41 shows a structure of a reception apparatus in accordance withthis exemplary embodiment.

FIG. 42 shows a structure of a reception apparatus in accordance withthis exemplary embodiment.

An operation of the transmission apparatus is demonstrated withreference to FIGS. 4, 12, and FIG. 43 through FIG. 49.

In FIG. 12, frame structure signal generator 1217 outputs theinformation about the frame structure shown in FIG. 43, FIG. 44, or FIG.45 as frame structure signal 1218. Modulation signal generator 1202 ofspread-spectrum communication method A receives frame structure signal1218 and transmission digital signal 1201 of spread spectrumtransmission method A, then outputs modulation signal 1203 of method Ain accordance with the frame structure. Modulation signal generator 1210of method B receives frame structure signal 1218 and transmissiondigital signal 1209 of spread spectrum transmission method B, thenoutputs modulation signal 1211 of method B in accordance with the framestructure.

Operations of modulation signal generators 1202 and 1210 in the case ofthe frame structure shown in FIG. 43 are demonstrated with reference toFIG. 46. At a transmitter of spread-spectrum communication method A,guard-symbol transmission signal generator 4601 shown in FIG. 46receives frame structure signal 1320. When signal 1320 indicates theguard symbol, generator 4601 outputs in-phase component 4602 andquadrature-phase component 4603 of the guard symbol transmissionquadrature baseband signal.

Synchronous symbol transmission signal generator 4604 receives framestructure signal 1320. When signal 1320 indicates the synchronoussymbol, generator 4604 outputs in-phase component 4605, quadrature-phasecomponent 4606 of the transmission quadrature baseband signal of thesynchronous symbol.

FIG. 4 shows the signal-point placement of the respective symbols in anin-phase-quadrature plane of the foregoing operation. Points 401 in FIG.4 indicate the signal-points of in-phase components 1311, 1318 andquadrature-phase component 1312, 1319 of the transmission quadraturebaseband signal of the data symbol. Points 402 indicate thesignal-points of in-phase component 4605 and quadrature-phase component4606 of the transmission quadrature baseband signal of the synchronoussymbol. Point 403 indicates the signal-points of in-phase component 4602and quadrature-phase component 4603 of the transmission quadraturebaseband signal of the guard symbol.

Operations of modulation signal generators 1202, 1210 in the case of theframe structure shown in FIG. 44 are demonstrated with reference to FIG.47 taking the transmitters of spread spectrum communication methods Aand B as examples.

FIG. 47 shows a detailed structure of modulation signal generator 1202at the transmitter of method A. Guard symbol or synchronous symbolmodulation signal generator 4701 receives frame structure signal 1320,and outputs in-phase component 4702, quadrature-phase component 4703 ofa transmission quadrature baseband signal of the guard symbol or thesynchronous symbol when signal 1320 indicates the synchronous symbol.

FIG. 47 shows a detailed structure of modulation signal generator 1202at the transmitter of method B. Guard symbol or synchronous symbolmodulation signal generator 4701 receives frame structure signal 1320,and outputs in-phase component 4702, quadrature-phase component 4703 ofa transmission quadrature baseband signal of the guard symbol or thesynchronous symbol when signal 1320 indicates the guard symbol.

FIG. 4 shows the signal-point placement of the respective symbols in anin-phase-quadrature plane of the foregoing operation. Points 401 in FIG.4 indicate the signal-points of in-phase components 1311, 1318 andquadrature-phase component 1312, 1319 of the transmission quadraturebaseband signal of the data symbol. Points 402 indicate thesignal-points of the in-phase component and the quadrature-phasecomponent of the transmission quadrature baseband signal of thesynchronous symbol. Point 403 indicates the signal-points of thein-phase component and the quadrature-phase component of thetransmission quadrature baseband signal of the guard symbol.

Operations of modulation signal generators 1202, 1210 in the case of theframe structure shown in FIG. 45 are demonstrated with reference toFIGS. 48, 49 taking the transmitters of spread spectrum communicationmethods A and B as examples.

FIG. 48 shows a detailed structure of modulation signal generator 1202at the transmitter of method A. Primary modulator 4802 shown in FIG. 48receives control information 4801, frame structure signal 1320, andoutputs in-phase component 4803, quadrature-phase component 4804 of atransmission quadrature baseband signal of the control information.

Synchronous symbol transmission signal generator 4805 receives framestructure signal 1320. When signal 1320 indicates the synchronoussymbol, generator 4805 outputs in-phase component 4806, quadrature-phasecomponent 4807 of the transmission quadrature baseband signal of thesynchronous symbol.

Spread unit 4808 receives in-phase component 4803 and quadrature-phasecomponent 4804 of the quadrature baseband signal of the controlinformation, in-phase component 4806, quadrature-phase component 4807 ofthe transmission quadrature baseband signal of the synchronous symbol,spread code 1317, frame structure signal 1320. Spread unit 4808 thenmultiplies code 1317 by the transmission quadrature baseband signal ofthe symbol indicated by frame structure signal 1320, and outputsin-phase component 4809 and quadrature-phase component 4810 of atransmission quadrature baseband signal of a control channel undergonethe spread.

FIG. 49 shows a detailed structure of guard symbol modulation signalgenerator 1212 at the transmitter of method B. Guard symbol modulationsignal generator 4901 receives frame structure signal 1320. When signal1320 indicates the guard symbol, generator 4901 outputs in-phasecomponent 4902, quadrature-phase component 4903 of a transmissionquadrature baseband signal of the guard symbol.

Spread unit 4808 receives the following signals:

-   -   in-phase component 4803 and quadrature-phase component 4804 of        the transmission quadrature baseband signal;    -   in-phase component 4902, quadrature-phase component 4903 of the        guard symbol transmission quadrature baseband signal;    -   spread code 1317; and    -   frame structure signal 1320.

Spread unit 4808 then multiplies spread code 1317 by the transmissionquadrature baseband signal of the symbol indicated by frame structuresignal 1320, and outputs in-phase component 4809 and quadrature-phasecomponent 4810 of a transmission quadrature baseband signal of thecontrol channel.

FIG. 4 shows the signal-point placement of the respective symbols in anin-phase-quadrature plane of the foregoing operation. Points 401 in FIG.4 indicate the signal-points of in-phase components and quadrature-phasecomponents of the data symbol and the control symbol. Points 402indicate the signal-points of the in-phase component and thequadrature-phase component of the transmission quadrature basebandsignal of the synchronous symbol. Point 403 indicates the signal-pointsof the in-phase component and the quadrature-phase component of thetransmission quadrature baseband signal of the guard symbol.

An operation of the reception apparatus is demonstrated with referenceto FIG. 37 through FIG. 42, in those drawings, demodulators 3723, 3725carries out demodulation following the spread-spectrum communicationmethod, namely, carries out inverse spread, then carries outdemodulation.

In the foregoing discussion, the received signal strength intensity isused as an example of a parameter of the radio-wave propagationenvironment; however, this embodiment is not limited to this example,and Doppler frequency or the number of paths of multi-path can be usedas the parameter.

The foregoing discussion proves that the transmission apparatus can besynchronized with the reception apparatus time-wise.

In this embodiment, the number of channels to be multiplexed are two;however, other numbers can be applicable to the embodiment. The framestructure is not limited to what is shown in FIG. 43, FIG. 44, or FIG.45. Both of spread-spectrum communication methods A and B use twochannels multiplied; however, they are not limited to the two channels.

The synchronous symbols shown in FIGS. 43, 44 and 45 are used fortime-synchronizing the reception apparatus with the transmissionapparatus; however, the symbols are not limited to this usage, and theycan be used for, e.g., estimating a frequency offset between thereception apparatus and the transmission apparatus.

The structure of the transmission apparatus of this embodiment is notlimited to what is shown in FIGS. 12, 13, and when the number ofspread-spectrum communication methods increases, the structure formed ofelements 1201 through 1208 shown in FIG. 12 are added accordingly. Whenthe number of channels increases, elements 1306, 1309 in FIG. 13increase accordingly.

The expression of “antenna” in the previous description does not alwaysmean a single antenna, but “antenna” can mean an antenna unit which isformed of a plurality of antennas.

The ninth exemplary embodiment, as discussed above, describes thetransmission method of transmitting modulation signals of a plurality ofchannels to the same frequency band from a plurality of antennas, moreparticularly, the method of transmitting the synchronous symbol in thespread-spectrum transmission method. The ninth embodiment also describesthe transmission apparatus and the reception apparatus to be used in theforegoing transmission method. The foregoing structure and operationallows increasing the data transmission rate, and synchronizing thetransmission apparatus with the reception apparatus time-wise.

Exemplary Embodiment 10

The tenth exemplary embodiment describes a transmission method oftransmitting modulation signals of a plurality of channels to the samefrequency band from a plurality of antennas, more particularly, a methodof transmitting a synchronous symbol in accordance with OFDM method. Thetenth embodiment also describes a transmission apparatus and a receptionapparatus to be used in the foregoing method.

FIG. 4 shows a placement of signal points in the in-phase-quadratureplane in accordance with this embodiment.

FIG. 25 shows a structure of the transmission apparatus in accordancewith this embodiment.

FIG. 50 shows a frame structure along a frequency-axis in accordancewith this embodiment, and to be more specific, it shows frame structure5010 of channel A and frame structure 5020 of channel B. Framestructures 5010, 5020 include synchronous symbol 5001, data symbols5002.

FIG. 51 shows a frame structure along a frequency-axis in accordancewith this embodiment, and to be more specific, it shows frame structure5110 of channel A and frame structure 5120 of channel B. Framestructures 5110, 5120 include synchronous symbol 5101, data symbols5102.

FIG. 52 shows a structure of the reception apparatus in accordance withthis embodiment, and the elements operating in a similar way to those inFIG. 26 have the same reference marks.

Synchronizing unit 5201 receives reception quadrature baseband signal2604, then synchronizes with the transmission apparatus time-wise, andoutputs timing signal 5204.

Synchronizing unit 5203 receives reception quadrature baseband signal2614, then synchronizes with the transmission apparatus time-wise, andoutputs timing signal 5204.

FIG. 53 shows a structure of the reception apparatus in accordance withthis embodiment, and the elements operating in a similar way to those inFIG. 26 have the same reference marks.

Synchronizing unit 5301 receives reception quadrature baseband signal2604, then synchronizes with the transmission apparatus time-wise, andoutputs timing signal 5302.

FIG. 54 shows a structure of the reception apparatus in accordance withthis embodiment, and the elements operating in a similar way to those inFIG. 37, or FIG. 39 have the same reference marks.

Discrete Fourier transformer 5401 receives reception quadrature basebandsignal 3704, timing signal 3914 selected, then outputs signal 5402undergone the discrete Fourier transformation.

In a similar way, discrete Fourier transformer 5403 receives receptionquadrature baseband signal 3709, timing signal 3914 selected, thenoutputs signal 5404 undergone the discrete Fourier transformation.

Discrete Fourier transformer 5405 receives reception quadrature basebandsignal 3715, timing signal 3914 selected, then outputs signal 5406undergone the discrete Fourier transformation.

FIG. 55 shows a structure of the reception apparatus in accordance withthis embodiment, and the elements operating in a similar way to those inFIG. 37, FIG. 39, FIG. 40 or FIG. 50 have the same reference marks.

FIG. 56 shows a structure of the reception apparatus in accordance withthis embodiment, and the elements operating in a similar way to those inFIG. 37, FIG. 39, or FIG. 54 have the same reference marks.

FIG. 57 shows a structure of the reception apparatus in accordance withthis embodiment, and the elements operating in a similar way to those inFIG. 37, FIG. 39, FIG. 40 or FIG. 54 have the same reference marks.

An operation of the transmission apparatus is demonstrated hereinafterwith reference to FIGS. 4, 25, 50 and 51. First, the transmissionapparatus that transmits modulation signals having the frame structureshown in FIG. 25 is described.

Frame structure signal generator 2521 shown in FIG. 25 outputs theinformation about the frame structure shown in FIG. 50 as framestructure signal 2522.

In FIG. 50, a synchronous symbol is transmitted through channel A attime 0, no signal is transmitted through channel B, in other words, thesignal is indicated by signal point 403 shown in FIG. 4. In a similarmanner, when a synchronous symbol is transmitted through channel B attime 1, no signal is transmitted through channel A, in other words, thesignal is indicated by signal point 403 shown in FIG. 4.

An operation of the transmission apparatus, which transmits a modulationsignal having the frame structure shown in FIG. 51, is demonstratedhereinafter. Frame structure signal generator 2521 shown in FIG. 25outputs the information about the frame structure shown in FIG. 51 asframe structure signal 2522. In FIG. 55, a synchronous symbol istransmitted through channel A at time 0, no signal is transmittedthrough channel B, in other words, the signal is indicated by signalpoint 403 shown in FIG. 4.

Next, an operation of the reception apparatus in accordance with thisembodiment is demonstrated with reference to FIG. 50 through FIG. 57.

In FIG. 52, synchronizing unit 5201 receives reception quadraturebaseband signal 2604, then detects the synchronous symbol transmitted asshown in FIG. 50 or FIG. 51 for synchronizing with the transmissionapparatus time-wise, and outputs timing signal 5202.

Discrete Fourier transformer 2605 receives reception quadrature basebandsignal 2604, timing signal 5202, then provides base-band signal 2604with discrete Fourier transformation based on timing signal 5202, andoutputs signal 2606 undergone the discrete Fourier transformation.

Synchronizing unit 5203 receives reception quadrature baseband signal2614, then detects the synchronous symbol transmitted as shown in FIG.50 or FIG. 51 for synchronizing with the transmission apparatustime-wise, and outputs timing signal 5204.

Discrete Fourier transformer 2615 receives reception quadrature basebandsignal 2614, timing signal 5204, then provides base-band signal 2614with discrete Fourier transformation based on timing signal 5204, andoutputs signal 2616 undergone the discrete Fourier transformation.

In FIG. 53, synchronizing unit 5301 receives reception quadraturebaseband signal 2604, then detects the synchronous symbol transmitted asshown in FIG. 50 or FIG. 51 for synchronizing with the transmissionapparatus time-wise, and outputs timing signal 5302.

Discrete Fourier transformer 2605 receives reception quadrature basebandsignal 2604, timing signal 5302, then provides base-band signal 2604with discrete Fourier transformation based on timing signal 5302, andoutputs signal 2606 undergone the discrete Fourier transformation.

Discrete Fourier transformer 2615 receives reception quadrature basebandsignal 2614, timing signal 5302, then provides base-band signal 2614with discrete Fourier transformation based on timing signal 5302, andoutputs signal 2616 undergone the discrete Fourier transformation.

In FIG. 54, discrete Fourier transformer 5401 receives receptionquadrature baseband signal 3704, timing signal 3914 received by theantenna having the best electric field, then provides base-band signal3704 with discrete Fourier transformation based on timing signal 3914,and outputs signal 5402 undergone the discrete Fourier transformation.

In a similar way to what is discussed above, discrete Fouriertransformer 5403 receives reception quadrature baseband signal 3709,timing signal 3914 received by the antenna having the best electricfield, then provides base-band signal 3709 with discrete Fouriertransformation based on timing signal 3914, and outputs signal 5404undergone the discrete Fourier transformation.

Discrete Fourier transformer 5405 receives reception quadrature basebandsignal 3715, timing signal 3914 received by the antenna having the bestelectric field, then provides base-band signal 3715 with discreteFourier transformation based on timing signal 3914, and outputs signal5406 undergone the discrete Fourier transformation.

In FIG. 55, discrete Fourier transformer 5401 receives receptionquadrature baseband signal 3704, timing signal 4004 received by theantenna having the best electric field, then provides base-band signal3704 with discrete Fourier transformation based on timing signal 4004,and outputs signal 5402 undergone the discrete Fourier transformation.

In a similar way to what is discussed above, discrete Fouriertransformer 5403 receives reception quadrature baseband signal 3709,timing signal 4004 received by the antenna having the best electricfield, then provides base-band signal 3709 with discrete Fouriertransformation based on timing signal 4004, and outputs signal 5404undergone the discrete Fourier transformation.

Discrete Fourier transformer 5405 receives reception quadrature basebandsignal 3715, timing signal 4004 received by the antenna having the bestelectric field, then provides base-band signal 3715 with discreteFourier transformation based on timing signal 4004, and outputs signal5406 undergone the discrete Fourier transformation.

In a similar way to what is discussed above, discrete Fouriertransformer 5403 receives reception quadrature baseband signal 3709,timing signal 3914 received by the antenna having the best electricfield, then provides base-band signal 3709 with discrete Fouriertransformation based on timing signal 3914, and outputs signal 5404undergone the discrete Fourier transformation.

Discrete Fourier transformer 5405 receives reception quadrature basebandsignal 3715, timing signal 3914 received by the antenna having the bestelectric field, then provides base-band signal 3715 with discreteFourier transformation based on timing signal 3914, and outputs signal5406 undergone the discrete Fourier transformation.

In FIG. 57, discrete Fourier transformer 5401 receives receptionquadrature baseband signal 3704, timing signal 4004 received by theantenna having the best electric field, then provides base-band signal3704 with discrete Fourier transformation based on timing signal 4004,and outputs signal 5402 undergone the discrete Fourier transformation.

In a similar way to what is discussed above, discrete Fouriertransformer 5403 receives reception quadrature baseband signal 3709,timing signal 4004 received by the antenna having the best electricfield, then provides base-band signal 3709 with discrete Fouriertransformation based on timing signal 4004, and outputs signal 5404undergone the discrete Fourier transformation.

Discrete Fourier transformer 5405 receives reception quadrature basebandsignal 3715, timing signal 4004 received by the antenna having the bestelectric field, then provides base-band signal 3715 with discreteFourier transformation based on timing signal 4004, and outputs signal5406 undergone the discrete Fourier transformation.

In the foregoing discussion, the received signal strength intensity isused as an example of a parameter of the radio-wave propagationenvironment; however, this embodiment is not limited to this example,and Doppler frequency or the number of paths of multi-path can be usedas the parameter.

The foregoing discussion proves that the transmission apparatus can besynchronized with the reception apparatus time-wise.

In this embodiment, two transmission antennas are used for thedescription purpose; however, this embodiment is not limited to the twoantennas, and two channels are multiplexed for the description purpose;however, this embodiment is not limited to the two channels. Framestructures are not limited to those shown in FIG. 50 and FIG. 51.

The synchronous symbols shown in FIGS. 50, 51 are used fortime-synchronizing the reception apparatus with the transmissionapparatus; however, the symbols are not limited to this usage, and theycan be used for, e.g., estimating a frequency offset between thereception apparatus and the transmission apparatus.

The structure of the transmission apparatus of this embodiment is notlimited to the one shown in FIG. 25, and the structure of the receptionapparatus of this embodiment is not limited to the ones shown in FIG. 52through FIG. 57.

The expression of “antenna” in the previous description does not alwaysmean a single antenna, but “antenna” can mean an antenna unit which isformed of a plurality of antennas.

The tenth exemplary embodiment, as discussed above, describes thetransmission method of transmitting modulation signals of a plurality ofchannels to the same frequency band from a plurality of antennas, moreparticularly, the method of transmitting a synchronous symbol inaccordance with OFDM method. The tenth embodiment also describes thetransmission apparatus and the reception apparatus to be used in theforegoing method. The structure and the operation discussed above allowsincreasing the data transmission rate, and synchronizing thetransmission apparatus with the reception apparatus time-wise.

Exemplary Embodiment 11

The 11th exemplary embodiment describes a transmission method oftransmitting modulation signals of a plurality of channels to the samefrequency band from a plurality of antennas, more particularly, areception apparatus which is applicable to a method of transmitting asignal including a control symbol.

FIGS. 33, 34, FIGS. 43-45, and FIGS. 50, 51 show a frame structure inaccordance with this embodiment. FIG. 58 shows a structure of thereception apparatus in accordance with the 11th embodiment, and theelements operating in a similar way to those in FIG. 37 have the samereference marks.

Frequency offset estimation unit 5801 receives reception quadraturebaseband signal 3715, then estimates a frequency offset with respect toa transmission apparatus, and outputs frequency offset estimation signal5802.

Frequency offset estimation unit 5803 receives reception quadraturebaseband signal 5802, then provides signal 5804 with frequency control,and outputs, e.g., signal 5804 which becomes a source signal of a radiounit.

FIG. 59 shows a structure of the reception apparatus in accordance withthis embodiment, and the elements operating in a similar way to those inFIG. 37 have the same reference marks.

Frequency offset estimation unit 5901 receives reception quadraturebaseband signal 3704, then estimates a frequency offset, and outputsfrequency offset estimation signal 5902.

Frequency offset estimation unit 5903 receives reception quadraturebaseband signal 3709, then estimates a frequency offset, and outputsfrequency offset estimation signal 5904.

Frequency offset estimation unit 5905 receives reception quadraturebaseband signal 3715, then estimates a frequency offset, and outputsfrequency offset estimation signal 5906.

Calculation unit 5907 receives frequency offset signals 5902, 5904,5906, then, e.g., averages those signals, and outputs frequency offsetestimation signal 5908 averaged.

Frequency controller 5909 receives averaged signal 5908, then outputs,e.g., signal 5910 to be a source signal of the radio unit.

FIG. 60 shows a structure of the reception apparatus in accordance withthis embodiment, and the elements operating in a similar way to those inFIG. 37 or FIG. 39 have the same reference marks.

Frequency offset estimation unit 6001 receives reception quadraturebaseband signal 3704, then estimates a frequency offset, and outputsfrequency offset estimation signal 6002.

Frequency offset estimation unit 6003 receives reception quadraturebaseband signal 3709, then estimates a frequency offset, and outputsfrequency offset estimation signal 6004.

Frequency offset estimation unit 6005 receives reception quadraturebaseband signal 3715, then estimates a frequency offset, and outputsfrequency offset estimation signal 6006.

Calculation unit 6007 receives frequency offset signals 6002, 6004,6006, and received signal strength intensity estimation signals 3902,3904, 3906, then weights those signals with the received signal strengthintensity, and averages the frequency offset signals, then outputsfrequency offset estimation signal 6008 averaged.

Frequency controller 6009 receives averaged signal 6008, then outputs,e.g., signal 6010 to be a source signal of the radio unit.

FIG. 61 shows a structure of the reception apparatus in accordance withthis embodiment, and the elements operating in a similar way to those inFIG. 37 or FIG. 39 have the same reference marks.

Frequency offset estimation unit 6101 receives a reception quadraturebaseband signal selected, then estimates a frequency offset, and outputsfrequency offset estimation signal 6102.

Frequency controller 6103 receives frequency offset estimation signal6102, then outputs, e.g., signal 6104 to be a source signal of the radiounit.

FIG. 62 shows a structure of the reception apparatus in accordance withthis embodiment, and the elements operating in a similar way to those inFIG. 37, FIG. 39 or FIG. 60 have the same reference marks.

FIG. 63 shows a structure of the reception apparatus in accordance withthis embodiment, and the elements operating in a similar way to those inFIG. 37, FIG. 39, FIG. 40, or FIG. 61 have the same reference marks.

FIG. 64 shows a structure of the reception apparatus in accordance withthis embodiment, and the elements operating in a similar way to those inFIG. 26 have the same reference marks.

Frequency offset estimation unit 6401 receives reception quadraturebaseband signal 2604, then estimates a frequency offset, and outputsfrequency offset estimation signal 6402.

Frequency offset estimation unit 6403 receives reception quadraturebaseband signal 2614, then estimates a frequency offset, and outputsfrequency offset estimation signal 6404.

Calculation unit 6405 receives frequency offset signals 6402, 6404,then, e.g., averages those signals, and outputs frequency offsetestimation signal 6406 averaged.

Frequency controller 6407 receives averaged signal 6406, then outputs,e.g., signal 6408 to be a source signal of the radio unit.

FIG. 65 shows a structure of the reception apparatus in accordance withthis embodiment, and the elements operating in a similar way to those inFIG. 26 have the same reference marks.

Frequency offset estimation unit 6501 receives reception quadraturebaseband signal 2604, then estimates a frequency offset, and outputsfrequency offset estimation signal 6502.

Frequency controller 6503 receives frequency offset estimation signal6502, then outputs, e.g., signal 6504 to be a source signal of the radiounit.

FIG. 66 shows a structure of the reception apparatus in accordance withthis embodiment, and the elements operating in a similar way to those inFIG. 37, FIG. 39, or FIG. 54 have the same reference marks.

Frequency offset estimation unit 6601 receives reception quadraturebaseband signal 3704, then estimates a frequency offset, and outputsfrequency offset estimation signal 6602.

Frequency offset estimation unit 6603 receives reception quadraturebaseband signal 3709, then estimates a frequency offset, and outputsfrequency offset estimation signal 6604.

Frequency offset estimation unit 6605 receives reception quadraturebaseband signal 3715, then estimates a frequency offset, and outputsfrequency offset estimation signal 6606.

Calculation unit 6607 receives frequency offset signals 6602, 6604,6606, and received signal strength intensity estimation signals 3902,3904, 3906, then weights those signals with the received signal strengthintensity, and averages the frequency offset signals, then outputsfrequency offset estimation signal 6608 averaged.

Frequency controller 6609 receives averaged signal 6608, then outputs,e.g., signal 6610 to be a source signal of the radio unit.

FIG. 67 shows a structure of the reception apparatus in accordance withthis embodiment, and the elements operating in a similar way to those inFIG. 37, FIG. 39, FIG. 40 or FIG. 54 have the same reference marks.

Frequency offset estimation unit 6701 receives reception quadraturebaseband signal 4002 selected, then estimates a frequency offset, andoutputs frequency offset estimation signal 6702.

Frequency controller 6703 receives frequency offset estimation signal6702, then outputs, e.g., signal 6704 to be a source signal of the radiounit.

FIG. 68 shows a structure of the reception apparatus in accordance withthis embodiment, and the elements operating in a similar way to those inFIG. 37, FIG. 39, FIG. 54 or FIG. 66 have the same reference marks.

FIG. 69 shows a structure of the reception apparatus in accordance withthis embodiment, and the elements operating in a similar way to those inFIG. 37, FIG. 39, FIG. 40, FIG. 54 or FIG. 67 have the same referencemarks.

Next, in the transmission method of transmitting modulation signals of aplurality of channels to the same frequency band from a plurality ofantennas, a reception apparatus, which is applicable to a method oftransmitting a signal including a control symbol, is describedhereinafter.

Examples of the frame structure in accordance with this embodiment areshown in FIGS. 33, 34, 43, 44, 45, 50 and 51. The reception apparatususes, e.g., a synchronous symbol, for estimating a frequency offset. Inthis case, the transmission apparatus has only one frequency source, sothat signals transmitted from the respective antennas are synchronizedin frequency with each other.

An operation of the reception apparatus shown in FIG. 58 is demonstratedhereinafter. Frequency offset estimation unit 5801 receives receptionquadrature baseband signal 3715, then estimates a frequency offset fromthe synchronous symbol, and outputs a frequency offset estimationsignal.

Demodulators 3723, 3725 removes the frequency offset from frequencyoffset estimation signal 5802 supplied.

Frequency controller 5803 receives frequency offset estimation signal5802, then removes the frequency offset therefrom, and outputs sourcesignal 5804 of the radio unit.

Next, operations of the reception apparatus shown in FIG. 59 differentfrom those described in FIG. 58 are demonstrated. Calculation unit 5907receives frequency offset estimation signals 5902, 5904, 5906, thenaverages those signals, and outputs frequency offset signal 5908averaged. This averaging of the signals can produce a more accurateestimation of the frequency offset.

Next, operations of the reception apparatus shown in FIG. 60 differentfrom those described in FIG. 58 are demonstrated. Calculation unit 6007receives received signal strength intensity estimation signals 3902,3904, 3906, and frequency offset estimation signals 6002, 6004, 6006,then weights those signals in response to the received signal strengthintensity, and outputs a frequency offset estimation signal averaged.This operation allows increasing the reliability of the frequency offsetestimation signal having strong received signal strength intensity, sothat more accurate estimation of the frequency offset can be expected.

Next, operations of the reception apparatus shown in FIG. 61 differentfrom those described in FIG. 58 are demonstrated. Signal selection unit4001 outputs a reception quadrature baseband signal having strongreceived signal strength intensity as signal 4002, so that frequencyoffset estimation unit 6101 produces more accurate estimation of thefrequency offset.

FIGS. 62, 63 differ from FIGS. 60, 61 in finding the received signalstrength intensity from the reception quadrature baseband signal.

As discussed above, in the method of transmitting modulation signals ofa plurality of channels to the same frequency band from a plurality ofantennas, and in the reception apparatus used in the spread-spectrumcommunication method, the frequency offset can be removed.

FIG. 64 through FIG. 69 show structures of the reception apparatus usedin OFDM transmission method, and the reception apparatus operates in asimilar way to what are shown in FIG. 58 through FIG. 63.

In the method of transmitting modulation signals of a plurality ofchannels to the same frequency band from a plurality of antennas, and inthe reception apparatus used in the OFDM transmission method, thefrequency offset can be removed according to the foregoing structure andoperation.

As a result, the frequency offset can be removed from both of thetransmission apparatus and the reception apparatus.

In this embodiment, the frame structure is not limited to what is shownin FIG. 33, 34, 43, 44, 45, 50 or 51.

In the transmission apparatus and the reception apparatus, the sourcesignal supplied to the radio unit can be commonly used by the respectiveradio units equipped to the respective antennas, so that the frequencyoffset can be commonly estimated to the plurality of antennas.

Similarly, in the transmission apparatus and the reception apparatus,production of modulation signals in the transmission apparatus as wellas the source signal for synchronizing in the reception apparatus can becommonly used by the respective modulation signal generators andsynchronizing units equipped to the respective antennas. As a result,time-synchronization can be done commonly to the plurality of antennas.

The expression of “antenna” in the previous description does not alwaysmean a single antenna, but “antenna” can mean an antenna unit which isformed of a plurality of antennas.

The 11th exemplary embodiment, as discussed above, describes thetransmission method of transmitting modulation signals of a plurality ofchannels to the same frequency band from a plurality of antennas, moreparticularly, the reception apparatus which is used in the method oftransmitting a signal including a control symbol. The structure andoperation discussed above allow increasing a data transmission rate, andallow the reception apparatus to remove frequency-offset.

Exemplary Embodiment 12

The 12th exemplary embodiment describes the following method andapparatus:

-   -   a communication method of transmitting a modulation signal to a        receiver, who receives the modulation signal then estimates        radio-wave propagation environment of respective antennas, and        transmits the estimated information of the radio-wave        propagation environment, then the communication method selecting        one of the following transmission methods based on the estimated        information:    -   a method of transmitting the modulation signals of a plurality        of channels to the same frequency band from the plurality of        antennas; or    -   a method of transmitting the modulation signal of one channel        from one antenna, and    -   a radio communication apparatus using the foregoing        communication method.

The 12th exemplary embodiment further describes the following method andapparatus:

-   -   a communication method of transmitting a modulation signal to a        receiver, who receives the modulation signal then estimates        radio-wave propagation environment of respective antennas, then        the communication method sending the information which requires        one of the following transmission methods based on the estimated        information of the radio-wave propagation environment:    -   a method of transmitting the modulation signals of a plurality        of channels to the same frequency band from the plurality of        antennas, or    -   a method of transmitting the modulation signal of one channel        from one antenna;    -   then the communication method selecting, based on the requiring        information, one of the foregoing two transmission methods, and    -   a radio communication apparatus using the foregoing        communication method.

FIG. 4 shows a placement of signal points in in-phase-quadrature (I-Q)plane. FIG. 70 shows a frame structure in accordance with thisembodiment along a time axis, to be more specific, frame structure 7040of a signal transmitted from a base station and frame structure 7050 ofa signal transmitted from a terminal. As shown in FIG. 70, framestructure 7040 includes frame structure 7020 of channel A and framestructure 7030 of channel B.

Frame structure 7020 includes information symbols 7001, 7003, 7004,7005, and guard symbol 7002 of the signal of channel A transmitted fromthe base station. Frame structure 7030 includes information symbols7007, 7009, guard symbols 7006, 7008, 7010 of the signal of channel Btransmitted from the base station. Frame structure 7050 includesinformation symbols 7011, 7012, 7013 of the signal transmitted from theterminal.

FIG. 71 shows information symbol structure 7110 of channel A signaltransmitted from the base station in accordance with this embodiment.Structure 7110 includes multiplex information symbol 7101 and datasymbol 7102.

FIG. 72 shows information symbol structure 7210 of a signal transmittedfrom the terminal in accordance with this embodiment. Structure 7210includes received signal strength intensity information symbol 7201,transmission path variation information symbol 7202, multi-pathinformation symbol 7203, disturbance information symbol 7204, and datasymbol 7205.

FIG. 73 shows information symbol structure 7310 of a signal transmittedfrom the terminal in accordance with this embodiment. Structure 7310includes transmission method requiring information symbol 7301, datasymbol 7302.

FIG. 74 shows a structure of a transmission apparatus at the basestation in accordance with this embodiment. The apparatus includeschannel A transmitter 7410, channel B transmitter 7420, and framestructure signal generator 209.

Channel A transmitter 7410 is formed of modulation signal generator 202,radio unit 204, power amplifier 206, and antenna 208.

Channel B transmitter 7420 is formed of modulation signal generator 212,radio unit 214, power amplifier 216, and antenna 218.

The elements operating in a similar way to those in FIG. 13 have thesame reference marks.

Modulation signal generator 202 receives transmission digital signal7401, multiplex information 7402, frame structure signal 210, andoutputs modulation signal 203 in accordance with the frame structure.

Frame structure signal generator 209 receives transmission methoddetermining information 7403, and outputs frame structure signal 210.

Modulation signal generator 212 receives transmission digital signal7401 and frame structure signal 210, then outputs modulation signal 213.

FIG. 75 shows a structure of a reception apparatus at the base station,and its radio unit 7503 receives signal 7502 received by antenna 7501,then outputs reception quadrature baseband signal 7504.

Demodulator 7505 receives reception quadrature baseband signal 7504,then outputs reception digital signal 7506.

Signal isolator 7507 receives signal 7506, and outputs radio-wavepropagation environmental information or transmission method requiringinformation 7508 and reception data 7509.

Transmission method determining unit 7510 receives radio-wavepropagation environmental information or transmission method requiringinformation 7508, then outputs transmission method determininginformation 7511 and multiplex information 7512.

FIG. 76 shows a structure of a transmission apparatus at the terminal inaccordance with this embodiment. Modulation signal generator 7606receives transmission digital signal 7601, radio-wave propagationenvironment estimation signals 7602, 7603, and frame structure signal7605, then outputs transmission quadrature baseband signal 7607.

Frame structure signal generator 7604 outputs frame structure signal7605.

Modulator 7608 receives transmission quadrature baseband signal 7607,then outputs modulation signal 7609 from antenna 7610 as radio wave.

FIG. 77 shows a structure of a reception apparatus at the terminal inaccordance with this embodiment. Radio unit 7703 receives signal 7702received by antenna 7701, then outputs reception quadrature basebandsignal 7704.

Multi-path estimation unit 7705 receives signal 7704, and outputsmulti-path estimation signal 7706.

Disturbance intensity estimation unit 7707 receives reception quadraturebaseband signal 7704, then outputs disturbance intensity estimationsignal 7708.

Received signal strength intensity estimation unit 7709 of channel Areceives reception quadrature baseband signal 7704, then outputsreceived signal strength intensity estimation signal 7710 of channel A.

Received signal strength intensity estimation unit 7711 of channel Breceives reception quadrature baseband signal 7704, then outputsreceived signal strength intensity estimation signal 7712 of channel B.

Transmission distortion estimation unit 7713 of channel A receivesreception quadrature baseband signal 7704, then outputs transmissionvariation estimation signal 7714 of channel A.

Transmission distortion estimation unit 7715 of channel B receivesreception quadrature baseband signal 7704, then outputs transmissionvariation estimation signal 7716 of channel B.

Information generator 7717 receives the following signals:

-   -   multi-path estimation signal 7706;    -   disturbance intensity estimation signal 7708;    -   received signal strength intensity estimation signal 7710 of        channel A;    -   received signal strength intensity estimation signal 7712 of        channel B;    -   transmission path variation estimation signal 7714 of channel A;        and    -   transmission path variation estimation signal 7716 of channel B,    -   then generator 7717 outputs radio wave propagation environment        estimation signal 7718.

Signal isolator 7719 receives the following signals:

-   -   reception quadrature baseband signals 7704, 7729;    -   transmission path variation estimation signals 7714, 7739 of        channel A; and    -   transmission path variation estimation signal 7716, 7741 of        channel B,    -   then isolator 7719 outputs reception quadrature baseband signals        7720, 7721 of channel A and channel B respectively.

Radio unit 7728 receives signal 7727 received by antenna 7726, thenoutputs reception quadrature baseband signal 7729.

Multi-path estimation unit 7730 receives reception quadrature basebandsignal 7729, and outputs multi-path estimation signal 7731.

Disturbance intensity estimation unit 7732 receives reception quadraturebaseband signal 7729, then outputs disturbance intensity estimationsignal 7733.

Received signal strength intensity estimation unit 7734 of channel Areceives reception quadrature baseband signal 7729, then outputsreceived signal strength intensity estimation signal 7735 of channel A.

Received signal strength intensity estimation unit 7736 of channel Breceives reception quadrature baseband signal 7729, then outputsreceived signal strength intensity estimation signal 7737 of channel B.

Transmission distortion estimation unit 7738 of channel A receivesreception quadrature baseband signal 7729, then outputs transmissionvariation estimation signal 7739 of channel A.

Transmission distortion estimation unit 7740 of channel B receivesreception quadrature baseband signal 7729, then outputs transmissionvariation estimation signal 7741 of channel B.

Information generator 7742 receives the following signals:

-   -   multi-path estimation signal 7731;    -   disturbance intensity estimation signal 7733;    -   received signal strength intensity estimation signal 7735 of        channel A;    -   received signal strength intensity estimation signal 7737 of        channel B;    -   transmission path variation estimation signal 7739 of channel A;        and    -   transmission path variation estimation signal 7741 of channel B,    -   then generator 7742 outputs radio wave propagation environment        estimation signal 7743.

FIG. 78 shows a structure of a transmission apparatus at the terminal inaccordance with this embodiment, and the elements operating in a similarway to those in FIG. 76 have the same reference marks.

Transmission method requiring information generator 7801 receivesradio-wave propagation environmental information 7602, 7603, thenoutputs transmission method requiring information 7802.

FIG. 84A shows a frame structure of a signal transmitted from the basestation in accordance with this embodiment, to be more specific, framestructure 8410 of channel A and frame structure 8420 of channel B.

FIG. 84B shows a frame structure of a signal transmitted from theterminal in accordance with this embodiment.

The base station transmits a modulation signal of OFDM method, and theframe structure includes guard symbol 8401 of the signal transmittedfrom the base station, information symbol 8402 of the signal transmittedfrom the base station, and information symbol 8403 of a signaltransmitted from the terminal.

Next, the following communication method is demonstrated with referenceto FIG. 4, and FIG. 70 through FIG. 77:

-   -   a communication method where a modulation signal is transmitted        to a receiver, who receives the modulation signal, estimates        radio-wave propagation environment of respective antennas, and        outputs the estimated information of the radio-wave propagation        environment, then the communication method selects one of the        following transmission methods based on the estimated        information:    -   a plurality of antennas transmit the modulation signals of a        plurality of channels to the same frequency band based on the        information, or    -   one antenna transmits the modulation signal of one channel.

A radio communication apparatus using the foregoing communication methodis also described hereinafter.

FIG. 74 shows the structure of the transmission apparatus at the basestation. Frame structure signal generator 7403 receives transmissionmethod determining information 7403. Based on information 7403,generator 7403 outputs, e.g., the information about one of the followingframe structures as frame structure signal 210:

-   -   a transmission method where information symbol 7004 of channel A        shown in FIG. 70 and the information symbol of channel B are        multiplexed; and    -   a transmission method where information symbol 7005 of channel A        shown in FIG. 70 is transmitted; however, channel B has guard        symbol 7010, so that they are not multiplexed.

Transmission determining information 7403 corresponds to output signal7511 from transmission method determining unit 7510.

Modulation signal generator 202 receives transmission digital signal7401, multiplex information 7402, and frame structure signal 210, thenoutputs modulation signal 203 of the information symbol. At this time,the information symbol is formed of multiplex information symbol 7101and data symbol 7102, as shown in FIG. 71. Multiplex information symbol7101 is a symbol of multiplex information 7402, and data symbol 7102 istransmission digital signal 7401. Multiplex information 7402 correspondsto output signal 7512 from the reception apparatus shown in FIG. 75 atthe base station.

Modulation signal generator 212 receives transmission digital signal7401, frame structure signal 210, and outputs modulation signal 213 ofthe guard symbol or the information symbol in response to framestructure signal 210, as shown in FIG. 70. At this time the modulationsignal of the guard symbol corresponds to signal point 403 shown in FIG.4.

FIG. 75 shows the structure of the reception apparatus at the basestation. Signal isolator 7507 isolates the following signals in theframe structure shown in FIG. 72:

-   -   data symbol 7205;    -   received signal strength intensity information symbol 7201        corresponding to the radio-wave propagation environmental        information;    -   transmission path variation information symbol 7202;    -   multi-path information symbol 7203; and    -   disturbance information symbol 7204.

Signal isolator 7507 then outputs the information of data symbol 7205 asreception data 7509, also outputs symbols 7201, 7202, 7203 and 7204 asradio-wave propagation environmental information 7508.

Transmission method determining unit 7510 receives information 7508, andbased on this information 7508, selects the communication method whichselects one of the following transmission methods:

-   -   a method of transmitting modulation signals of a plurality of        channels to the same frequency band from a plurality of        antennas; or    -   a method of transmitting a modulation signal of one channel from        one antenna.

Determining unit 7510 then outputs the information of the transmissionmethods as transmission method determining information 7511 andmultiplex information 7512.

FIG. 76 shows the transmission apparatus at the terminal. The apparatusreceives transmission digital signal 7601, radio-wave propagationenvironment estimation signals 7602, 7603, and frame structure signal7605. According to the frame structure shown in FIG. 72, signal 7601 istreated as data symbol 7205, signals 7602, 7603 are treated as receivedsignal strength intensity information symbol 7201, transmission pathvariation information symbol 7202, multi-path information symbol 7203,and disturbance information symbol 7204. Then the transmission apparatusoutputs modulation signal 7606. Radio-wave propagation estimationsignals 7602, 7603 correspond to radio-wave propagation environmentestimation signals 7718, 7743 of the reception apparatus shown in FIG.77 at the terminal.

FIG. 77 shows the structure of the reception apparatus at the terminal.Information generator 7717 receives the following signals:

-   -   multi-path estimation signal 7706;    -   disturbance intensity estimation signal 7708;    -   received signal strength intensity estimation signal 7710 of        channel A signals;    -   received signal strength intensity estimation signal 7712 of        channel B signals;    -   transmission path variation estimation signal 7714 of channel A;        and    -   transmission path variation estimation signal 7716 of channel B.

Generator 7717 then outputs radio-wave propagation environmentestimation signal 7718 corresponding to the information of receivedsignal strength intensity information symbol 7201, transmission pathvariation information symbol 7202, multi-path information symbol 7203,and disturbance information symbol 7204 shown in FIG. 72.

In a similar way to the foregoing operation, information generator 7742receives the following signals:

-   -   multi-path estimation signal 7731;    -   disturbance intensity estimation signal 7733;    -   received signal strength intensity estimation signal 7735 of        channel A signals;    -   received signal strength intensity estimation signal 7737 of        channel B signals;    -   transmission path variation estimation signal 7739 of channel A;        and    -   transmission path variation estimation signal 7741 of channel B.

Generator 7742 then outputs radio-wave propagation environmentestimation signal 7743 corresponding to the information of receivedsignal strength intensity information symbol 7201, transmission pathvariation information symbol 7202, multi-path information symbol 7203,and disturbance information symbol 7204 shown in FIG. 72.

In conclusion, depending on a radio-wave propagation environment, thetransmission method of transmitting modulation signals of a plurality ofchannels to the same frequency band from a plurality of antennas can beswitched to/from the transmission method of transmitting modulationsignals of a plurality of channels without multiplexing to the samefrequency band. This operation can improve the quality of information.

In the foregoing operation, radio-wave propagation environmentestimation signals 7718, 7743 correspond to signals 7602, 7603 of thetransmission apparatus shown in FIG. 76 at the terminal.

Next, an operation at starting a communication is demonstratedhereinafter. When the communication starts, the base station transmitsmodulation signals by the transmission method of transmitting modulationsignals of a plurality of channels to the same frequency band from aplurality of antennas. At this time, if the terminal is not suitable forthe foregoing transmission method, the quality of reception data islowered.

In order to avoid this problem, when a communication to the terminalstarts, the base station transmits modulation signals of a plurality ofchannels without multiplexing to the same frequency band as symbols7001, 7006, and symbols 7002, 7007 shown in FIG. 70.

Frame structure signal generator 209 shown in FIG. 74 outputs framestructure signal 210 in which the following frame structure is prepared:When a communication to the terminal starts, modulations signals of aplurality of channels are transmitted, without being multiplexed, to thesame frequency band as symbols 7001, 7006 and symbols 7002, 7007 shownin FIG. 70.

The reception apparatus shown in FIG. 77 at the terminal estimates aradio-wave propagation environment from the reception signal of symbols7001, 7007 transmitted from the base station, then generates radio-wavepropagation environment estimation signals 7718, 7743.

The transmission apparatus shown in FIG. 76 at the terminal transmitsestimation signals 7718, 7743 with information symbols 7011, 7012 shownin FIG. 70.

The reception apparatus shown in FIG. 75 at the terminal selects one ofthe following transmission methods based on the radio-wave propagationenvironment estimation information included in information symbol 7011which is a part of the signal transmitted from transmission apparatusshown in FIG. 76 at the terminal:

-   -   a method of transmitting modulation signals of a plurality of        channels to the same frequency band from a plurality of        antennas; or    -   a method of transmitting modulation signals of a plurality of        channels without being multiplexed to the same frequency band.

In the case of, e.g., a fine environment for the radio-wave propagation,the modulation signals of the plurality of channels are transmitted fromthe plurality of antennas such as information symbols 7004, 7009.

As discussed above, when the communication to the terminal starts,modulation signals of a plurality of channels are transmitted withoutbeing multiplexed to the same frequency band, thereby improving theinformation quality.

In the foregoing discussion, a modulation signal indicating that theterminal requires a communication to the base station can be transmittedat the beginning. When the base station uses the OFDM transmissionmethod, what is discussed above can be also used.

Next, a communication method, which selects one of the followingtransmission methods, and a radio communication apparatus using thiscommunication method Are described hereinafter with reference to FIGS.4, 70, 71, 73, 74, 75, 77 and 78. When a modulation signal istransmitted to a receiver, who receives the modulation signal andestimates radio-wave propagation environments of respective antennas,the communication method selects one of the following transmissionmethods based on the estimation:

-   -   a method of transmitting information that requires one of the        following two methods, and based on the information, this method        selects one of the transmission methods below:    -   a method of transmitting modulation signals of a plurality of        channels to the same frequency band from a plurality of        antennas; or    -   a method of transmitting a modulation signal of one channel from        one antenna.

FIG. 74 shows the structure of the transmission apparatus at the basestation. Frame structure signal generator 7403 receives transmissionmethod determining information 7403. Based on information 7403,generator 7403 outputs, e.g., the information about one of the followingframe structures as frame structure signal 210:

-   -   a frame structure of a transmission method where information        symbol 7004 of channel A shown in FIG. 70 and the information        symbol of channel B are multiplexed; or    -   a frame structure of a transmission method where information        symbol 7005 of channel A shown in FIG. 70 is transmitted;        however, channel B has guard symbol 7010, so that they are not        multiplexed.

Transmission determining information 7403 corresponds to output signal7511 from transmission method determining unit 7510.

Modulation signal generator 202 receives transmission digital signal7401, multiplex information 7402, and frame structure signal 210, thenoutputs modulation signal 203 of the information symbol. At this time,the information symbol is formed of multiplex information symbol 7101and data symbol 7102, as shown in FIG. 71. Multiplex information symbol7101 is a symbol of multiplex information 7402, and data symbol 7102 istransmission digital signal 7401. Multiplex information 7402 correspondsto output signal 7512 from the reception apparatus shown in FIG. 75 atthe base station.

Modulation signal generator 212 receives transmission digital signal7401, frame structure signal 210, and outputs modulation signal 213 ofthe guard symbol or the information symbol in response to framestructure signal 210, as shown in FIG. 70. At this time the modulationsignal of the guard symbol corresponds to signal point 403 shown in FIG.4.

FIG. 75 shows the structure of the reception apparatus. Signal isolator7507 isolates data symbol 7302 from transmission method requiringinformation symbol 7301 in the frame structure shown in FIG. 73, thenoutputs the information of data symbol 7205 as reception data 7509, andinformation symbol 7301 as transmission method requiring information7509.

Transmission method determining unit 7510 receives information 7508,then selects a communication method which selects one of thetransmission method of transmitting modulation signals of a plurality ofchannels to the same frequency band from a plurality of antennas, or atransmission method of transmitting a modulation signal of one channelfrom one antenna. Determining unit 7510 outputs the information aboutthe transmission method selected as transmission method determininginformation 7511 and multiplex information 7512.

FIG. 78 shows the structure of the transmission apparatus at theterminal. Transmission method requiring information generator 7801receives radio-wave propagation environment estimation signals 7602,7603. In response to those signals generator 7801 outputs acommunication method which selects one of the following two transmissionmethods as transmission requiring information 7802:

-   -   in the case of, e.g., a fine environment for the radio-wave        propagation, the transmission method of transmitting modulation        signals of a plurality of channels to the same frequency band        from a plurality of antennas.    -   in the case of, e.g., a bad environment for the radio-wave        propagation, the transmission method of transmitting a        modulation signal of one channel from one antenna.

Modulation signal generator 7606 receives transmission digital signal7601, frame structure signal 7605, and transmission requiringinformation 7802, and modulates signal 7601 and information 7802according to the frame structure shown in FIG. 73, then outputstransmission quadrature baseband signal 7607. Radio-wave propagationenvironment estimation signals 7602, 7603 correspond to radio-wavepropagation environment estimation signals 7718, 7743 of the receptionapparatus shown in FIG. 77 at the terminal.

FIG. 77 shows the structure of the reception apparatus at the terminal.Information generator 7717 receives the following signals:

-   -   multi-path estimation signal 7706;    -   disturbance intensity estimation signal 7708;    -   received signal strength intensity estimation signal 7710 of        channel A signals;    -   received signal strength intensity estimation signal 7712 of        channel B signals;    -   transmission path variation estimation signal 7714 of channel A;        and    -   transmission path variation estimation signal 7716 of channel B,    -   then generator 7717 outputs radio wave propagation environment        estimation signal 7718.

In a similar way to the foregoing operation, information generator 7742receives the following signals:

-   -   multi-path estimation signal 7731;    -   disturbance intensity estimation signal 7733;    -   received signal strength intensity estimation signal 7735 of        channel A signals;    -   received signal strength intensity estimation signal 7737 of        channel B signals;    -   transmission path variation estimation signal 7739 of channel A;        and    -   transmission path variation estimation signal 7743 of channel B,    -   then generator 7742 outputs radio wave propagation environment        estimation signal 7743.

Radio wave propagation environment estimation signals 7718, 7743correspond to signals 7602, 7603 of the transmission apparatus shown inFIG. 78 at the terminal.

In conclusion, depending on a radio-wave propagation environment, thetransmission method of transmitting modulation signals of a plurality ofchannels to the same frequency band from a plurality of antennas can beswitched to/from the transmission method of transmitting modulationsignals of a plurality of channels without multiplexing to the samefrequency band. This operation can increase the quality of information.

Next, an operation at starting a communication is demonstratedhereinafter. When the communication starts, the base station transmitsmodulation signals by the transmission method of transmitting modulationsignals of a plurality of channels to the same frequency band from aplurality of antennas. At this time, if the terminal is not suitable forthe foregoing transmission method, the quality of reception data islowered.

In order to avoid this problem, when a communication to the terminalstarts, the base station transmits modulation signals of a plurality ofchannels without multiplexing to the same frequency band as symbols7001, 7006, and symbols 7002, 7007 shown in FIG. 70.

Frame structure signal generator 209 shown in FIG. 74 outputs framestructure signal 210 in which the following frame structure is prepared:When a communication to the terminal starts, modulation signals of aplurality of channels are transmitted, without being multiplexed, to thesame frequency band as symbols 7001, 7006 and symbols 7002, 7007 shownin FIG. 70.

The reception apparatus shown in FIG. 77 at the terminal estimates aradio-wave propagation environment from the reception signal of symbols7001, 7007 transmitted from the base station, then generates radio-wavepropagation environment estimation signals 7718, 7743.

Transmission method requiring information generator 7801 of thetransmission apparatus shown in FIG. 78 at the terminal receivesradio-wave propagation environment estimation signals 7718, 7743 whichestimate the environment from the reception signal of symbols 7001, 7007transmitted from the base station. Generator 7801 then selects one ofthe following two transmission methods:

-   -   a method of transmitting modulation signals of a plurality of        channels to the same frequency band from a plurality of        antennas; or    -   a method of transmitting modulation signals of a plurality of        channels without being multiplexed to the same frequency band.

Generator 7801 outputs transmission requiring information 7802, which istransmitted in the structure of the information symbol of thetransmission signal shown in FIG. 73 in accordance with, e.g.,information symbol 7011 shown in FIG. 70.

The reception apparatus shown in FIG. 75 at the terminal selects one ofthe following transmission methods based on the transmission methodrequiring information symbol included in information symbol 7011 whichis a part of the signal transmitted from transmission apparatus shown inFIG. 78 at the terminal:

-   -   a method of transmitting modulation signals of a plurality of        channels to the same frequency band from a plurality of        antennas; or    -   a method of transmitting modulation signals of a plurality of        channels without being multiplexed to the same frequency band.

As discussed above, when the communication to the terminal starts,modulation signals of a plurality of channels are transmitted withoutbeing multiplexed to the same frequency band, thereby improving theinformation quality.

In the foregoing discussion, a modulation signal indicating that theterminal requires a communication to the base station can be transmittedat the beginning

In this embodiment, what is discussed previously is applicable to anyone of the following methods: single carrier method, spread-spectrumcommunication method, CDMA method (multiplexing method). In the case ofusing any one of those methods, the transmission apparatus needs aspread unit, and the reception apparatus needs an inverse-spread unit.

Hereinafter the case, where OFDM method Among others is employed, isdescribed. FIG. 84 shows a frame structure when the base stationtransmits signals by OFDM method. The transmission apparatus at the basestation transmits a modulation signal of channel A at time 0, and atthis time, the terminal receives the modulation signal transmitted bythe base station at time 0 as well as the modulation signal transmittedby the base station at time 1. The terminal then estimates a radio-wavepropagation environment such as multi-path, disturbance received signalstrength intensity, electric field intensities of channels A and Brespectively, and transmission path variations of channels A and Brespectively. The terminal transmits transmission requiring information,which requires one of the following information, to the base station:

-   -   the foregoing radio-wave propagation environment estimation        information;    -   a method of transmitting modulation signals of a plurality of        channels to the same frequency band from a plurality of        antennas; or    -   a method of transmitting modulation signals of a plurality of        channels without being multiplexed to the same frequency band.

The base station determines the transmission method based on theforegoing environment estimation information or the transmissionrequiring information. In the case of a fine environment for the radiowave propagation, channel A and channel B are multiplexed fortransmission such as time 3 and time 4 shown in FIG. 84. In the case ofa bad environment, a modulation signal of channel A only is transmittedsuch as time 5 in FIG. 84. In those cases, the transmission apparatusand the reception apparatus at the base station and the terminal can bestructured as shown in FIG. 74 through FIG. 78, which are described inthe frame structure shown in FIG. 70. What is discussed above is alsoapplicable to the case where a signal of the spread-spectrumcommunication method is modulated by OFDM method.

This embodiment refers to the case where two channels are multiplexed,or switched to the case where one channel is used without beingmultiplexed; however, this example does not limit the embodiment. Forinstance, in the case where three channels can be multiplexed to thesame frequency band, the transmission apparatus at the base stationswitches the number of multiplexing between 1-3 channels.

The expression of “antenna” in the previous description does not alwaysmean a single antenna, but “antenna” can mean an antenna unit which isformed of a plurality of antennas.

The 12th exemplary embodiment, as discussed above, proves that thefollowing method and apparatus are achievable:

-   -   a communication method of transmitting a modulation signal to a        receiver, who receives the modulation signal then estimates        radio-wave propagation environment of respective antennas, and        transmits the estimated information of the radio-wave        propagation environment, then the communication method selecting        one of the following transmission methods based on the estimated        information:    -   a method of transmitting the modulation signals of a plurality        of channels to the same frequency band from the plurality of        antennas; or    -   a method of transmitting the modulation signal of one channel        from one antenna, and    -   a radio communication apparatus using the foregoing        communication method.

This operation and apparatus allows switching between the foregoing twotransmission methods depending on the radio-wave propagationenvironment. As a result, the information can be transmitted moreaccurately.

Exemplary Embodiment 13

The 13th exemplary embodiment describes the following method, by whichmodulation signals of a plurality of spread-spectrum communicationmethods can be transmitted:

-   -   a communication method where a modulation signal of a        transmission method, by which a control channel is transmitted,        is transmitted to a receiver, who receives the modulation        signal, estimates radio-wave propagation environment of        respective antennas from reception signals of the control        channel, and transmits the estimated information of the        radio-wave propagation environment, then the communication        method selects one of the following transmission methods based        on the estimated information:    -   a method of transmitting the modulation signals of a plurality        of data channels of the plurality of spread-spectrum        communication methods to the same frequency band from a        plurality of antennas, or    -   a method of transmitting the modulation signal of one data        channel of one spread-spectrum communication method from one        antenna.

The 13th embodiment also describes a radio communication apparatus usingthe foregoing communication method.

The 13th exemplary embodiment further describes the following method, bywhich modulation signals of a plurality of spread-spectrum communicationmethods can be transmitted:

-   -   a communication method where a modulation signal of the        transmission method, by which a control channel is transmitted,        is transmitted to a receiver, who receives the modulation        signal, estimates radio-wave propagation environment of        respective antennas from reception signals of the control        channel, then the communication method sends the information        which requires one of the following transmission methods based        on the estimated information of the radio-wave propagation        environment:    -   a method of transmitting the modulation signals of a plurality        of data channels of the plurality of spread-spectrum        communication methods to the same frequency band from a        plurality of antennas, or    -   a method of transmitting the modulation signal of a data channel        of one spread-spectrum communication method from one antenna;    -   then the communication method selects, based on the requiring        information, one of the foregoing two transmission methods, and    -   a radio communication apparatus using the foregoing        communication method is also described.

FIG. 4 shows a placement of signal points on the in-phase-quadrature(I-Q) plane.

FIG. 73 shows a structure of an information symbol at a terminal inaccordance with this embodiment.

FIG. 75 shows a structure of a reception apparatus at a base station inaccordance with this embodiment.

FIG. 76 shows a structure of a transmission apparatus at the terminal inaccordance with this embodiment.

FIG. 78 shows a structure of a transmission apparatus at the terminal inaccordance with this embodiment.

FIG. 79 shows a frame structure along a time axis in accordance withthis embodiment, to be more specific, frame structure 7980 of a signaltransmitted from the base station and frame structure 7990 of a signaltransmitted from the terminal. One example of frame structure 7980includes the following frames:

-   -   frame structure 7960 of spread-spectrum communication method A,        where frame structure 7960 is formed of data channel 7920 and        control channel 7930, and    -   frame structure 7970 of spread-spectrum communication method B,        where frame structure 7970 is formed of data channel 7940 and        control channel 7950.

Frame structure 7920 includes information symbols 7901, 7902. Framestructure 7930 includes control symbols 7903, 7904, 7905, and 7906 ofmethod A.

Frame structure 7940 includes information symbols 7907, guard symbol7908. Frame structure 7950 includes control symbols 7909, 7910, 7911,and 7912 of method B.

Information symbols 7913, 7914, and 7915 belong to the signaltransmitted from the terminal.

FIG. 80 shows a structure of the transmission apparatus at the basestation in accordance with this embodiment. The apparatus includestransmitters 8020 and 8030 responsible for spread-spectrum communicationmethods A and B, respectively, and frame structure signal generator 209.

Transmitter 8020 of method A includes data-channel modulation and spreadunit 8002, control-channel modulation and spread unit 8006, adding unit8004, radio unit 204, power amplifier 206, and antenna 208.

Transmitter 8030 of method B includes data-channel modulation and spreadunit 8009, control-channel modulation and spread unit 8012, adding unit8011, radio unit 214, power amplifier 216, and antenna 218.

The elements operating in a similar way to those in FIG. 2 have the samereference marks.

Data-channel modulation and spread unit 8002 receives transmissiondigital signal 8001, frame structure signal 210, and outputstransmission quadrature baseband signal 8003 of the data channel ofmethod A.

Control-channel modulation and spread unit 8006 receives transmissionmethod determining information 8005, frame structure signal 210, andoutputs transmission quadrature baseband signal 8010 of the controlchannel of method A.

Adding unit 8004 receives base-band signals 8003 of data channel and8010 of control channel, then add those signals together, therebyoutputting transmission quadrature baseband signal 203.

Data-channel modulation and spread unit 8009 receives transmissiondigital signal 8008, frame structure signal 210, then outputstransmission quadrature baseband signal 8010 of the data channel ofmethod B.

Control-channel modulation and spread unit 8012 receives transmissionmethod determining information 8005, frame structure signal 210, thenoutputs transmission quadrature baseband signal 8013 of the controlchannel of method B.

Adding unit 8011 receives base-band signals 8010 of data channel and8013 of control channel, then add those signals together, therebyoutputting transmission quadrature baseband signal 213.

Frame structure signal generator 209 receives transmission methoddetermining information 8005, then outputs frame structure signal 210.

FIG. 81 shows a structure of control symbol 8110, and details astructure of control symbols 7903, 7904, 7905, 7906, 7909, 7910, 7911,and 7912 shown in FIG. 79.

Control symbol 8110 includes multiplex information 8101, pilot symbol8102, and transmission power control information 8103.

FIG. 82 shows a structure of a reception apparatus at the terminal inaccordance with this embodiment, and the elements operating in a similarway to those in FIG. 77 have the same reference marks.

Received signal strength intensity estimation unit 8201 of method Areceives reception quadrature baseband signal 7704, and outputs receivedsignal strength intensity estimation signal 8202 of method A.

Received signal strength intensity estimation unit 8203 of method Breceives reception quadrature baseband signal 7704, and outputs receivedsignal strength intensity estimation signal 8204 of method B.

Transmission path variation estimation unit 8205 of method A receivesreception quadrature baseband signal 7704, and outputs transmission pathvariation estimation signal 8206 of method A.

Transmission path variation estimation unit 8207 of method B receivesreception quadrature baseband signal 7704, and outputs transmission pathvariation estimation signal 8208 of method B.

Information generator 7717 receives the following signals:

-   -   multi-path estimation signal 7706;    -   disturbance intensity estimation signal 7708;    -   received signal strength intensity estimation signal 8202 of        method A signals;    -   received signal strength intensity estimation signal 8204 of        method B signals;    -   transmission path variation estimation signal 8206 of method A;        and    -   transmission path variation estimation signal 8208 of method B,    -   then generator 7717 outputs radio wave propagation environment        estimation signal 7718.

Received signal strength intensity estimation unit 8209 of method Areceives reception quadrature baseband signal 7729, and outputs electricfiled intensity estimation signal 8210 of method A.

Received signal strength intensity estimation unit 8211 of method Breceives reception quadrature baseband signal 7729, and outputs electricfiled intensity estimation signal 8212 of method B.

Transmission path variation estimation unit 8213 of method A receivesreception quadrature baseband signal 7729, and outputs transmission pathvariation estimation signal 8214 of method A.

Transmission path variation estimation unit 8215 of method B receivesreception quadrature baseband signal 7729, and outputs transmission pathvariation estimation signal 8216 of method B.

Information generator 7742 receives the following signals:

-   -   multi-path estimation signal 7731;    -   disturbance intensity estimation signal 7733;    -   received signal strength intensity estimation signal 8210 of        method A signals;    -   received signal strength intensity estimation signal 8212 of        method B signals;    -   transmission path variation estimation signal 8214 of method A;        and    -   transmission path variation estimation signal 8216 of method B,    -   then generator 7742 outputs radio wave propagation environment        estimation signal 7743.

FIG. 83 shows a frame structure in accordance with this embodiment, tobe more specific, frame structure 8301 of a signal transmitted from thebase station, and frame structure 8302 of a signal transmitted from theterminal. An example of frame structure 8301 includes frame structure8303 of method A, where structure 8303 is formed of data channel 8305and control channel 8306, and frame structure 8304 of method B, wherestructure 8304 is formed only data channel 8307.

FIG. 85 shows a structure of a control symbol of control channel 8510when the base station transmits a signal of spread-spectrumcommunication method by OFDM method. Control channel 8510 includescontrol symbols 8501 through 8504 along a time axis.

FIG. 86 shows a structure of a control symbol of control channel 8610when the base station transmits a signal of spread-spectrumcommunication method by OFDM method. Control channel 8610 includescontrol symbols 8601 through 8604 along a frequency axis.

Next, the following method, by which modulation signals of a pluralityof spread-spectrum communication methods can be transmitted, isdescribed with reference to FIGS. 4, 72, 75, 76, 79, 80, 81, and 82:

-   -   a communication method where a modulation signal of a        transmission method, which transmits a control channel, is        transmitted to a receiver, who receives the modulation signal,        estimates radio-wave propagation environment of respective        antennas from reception signals of the control channel, and        transmits the estimated information of the radio-wave        propagation environment, then the communication method selects        one of the following transmission methods based on the estimated        information:    -   a method of transmitting the modulation signals of a plurality        of data channels of the plurality of spread-spectrum        communication methods to the same frequency band from a        plurality of antennas, or    -   a method of transmitting the modulation signal of one data        channel of one spread-spectrum communication method from one        antenna.

A radio communication apparatus using the foregoing communication methodis also described hereinafter.

FIG. 80 shows a structure the transmission apparatus at the basestation. Frame structure signal generator 209 receives transmissionmethod determining information 8005, and based on information 8005,outputs the following frame structure information about one of thefollowing two transmission methods as frame structure signal 210:

-   -   a method, where, e.g., information symbol 7901 of method A and        information symbol 7907 of method B shown in FIG. 79 are        multiplexed together; or    -   a method, where, information symbol 7902 of method A is        transmitted; however, method B has guard symbol 7908, so that        they are not multiplexed.

Transmission method determining information 8005 corresponds toreception apparatus 7511 shown in FIG. 75 at the base station.

Data-channel modulation and spread unit 8002 receives transmissiondigital signal 8001, frame structure signal 210, then outputstransmission quadrature baseband signal 8003 of method A.

Data-channel modulation and spread unit 8009 receives transmissiondigital signal 8008, frame structure signal 210, then in response toframe structure signal 210, outputs base-band signal 8010 of method B ofthe guard symbol or the information symbol as shown in FIG. 79. At thistime, the modulation signal of the guard symbol is indicated by signalpoint 403 shown in FIG. 4.

Control channel modulation and spread unit 8006 receives transmissionmethod determining information 8005, then outputs transmissionquadrature baseband signal 8007 containing the control information forthe control channel which includes, as shown in FIG. 81, multiplexinformation 8101, pilot symbol 8102, and transmission power controlinformation 8103.

In a similar way to what is discussed above, control channel modulationand spread unit 8012 receives transmission method determininginformation 8005, then outputs transmission quadrature baseband signal8013 containing the control information for the control channel whichincludes, as shown in FIG. 81, multiplex information 8101, pilot symbol8102, and transmission power control information 8103.

Multiplex information 8101 shown in FIG. 81 works as a symbol fornotifying one of the following transmission methods to the terminal:

-   -   a method of multiplexing method A and method B together; or    -   a transmission method of transmitting method A only.

FIG. 75 shows a structure of the reception apparatus of the basestation. Signal isolator 7507 isolates data symbol 7205 from thefollowing elements corresponding to the radio-wave propagationenvironment information:

-   -   received signal strength intensity information symbol 7201;    -   transmission path variation information symbol 7202;    -   multi-path information symbol 7203; and    -   disturbance information symbol 7204.

Isolator 7507 then outputs the information of data symbol 7205 asreception data 7509. Isolator 7507 also outputs the information offoregoing symbols 7201 through 7204 as radio-wave propagationenvironment estimation information 7508.

Transmission method determining unit 7510 receives radio-wavepropagation environmental information, and based on this information,selects one of the following transmission methods:

-   -   a method of transmitting modulation signals of data channels of        a plurality of spread-spectrum communication methods to the same        frequency band from a plurality of antennas; or    -   a method of transmitting a modulation signal of a data channel        of one spread-spectrum communication method to the same        frequency band from one antenna.

Determining unit 7510 then outputs the information about thetransmission method as transmission method determining information 7511and multiplex information 7512.

FIG. 76 shows the structure of the transmission apparatus at theterminal. The apparatus receives transmission digital signal 7601,radio-wave propagation environment estimation signals 7602, 7603, andframe structure signal 7604. According to the frame structure shown inFIG. 72, signal 7601 is treated as data symbol 7205, signals 7602, 7603are treated as received signal strength intensity information symbol7201, transmission path variation information symbol 7202, multi-pathinformation symbol 7203, and disturbance information symbol 7204. Thenthe transmission apparatus outputs modulation signal 7606. Radio-wavepropagation estimation signals 7602, 7603 correspond to radio-wavepropagation environment estimation signals 7718, 7743 of the receptionapparatus shown in FIG. 82 at the terminal.

FIG. 82 shows a structure of the reception apparatus at the terminal.Received signal strength intensity estimation unit 8201 of method Areceives reception quadrature baseband signal 7704, and estimates areceived signal strength intensity from, e.g., a component of thecontrol channel shown in FIG. 79 of method A of reception quadraturebaseband signal 7704. Estimation unit 8201 then outputs received signalstrength intensity estimation signal 8202 of method A.

Received signal strength intensity estimation unit 8203 of method Breceives reception quadrature baseband signal 7704, and estimates areceived signal strength intensity from, e.g., a component of thecontrol channel shown in FIG. 79 of method B of reception quadraturebaseband signal 7704. Estimation unit 8203 then outputs received signalstrength intensity estimation signal 8204 of method B.

Transmission path variation estimation unit 8205 of method A receivesreception quadrature baseband signal 7704, and estimates a transmissionpath variation from, e.g., a component of the control channel shown inFIG. 79 of method A, then outputs transmission path variation estimationsignal 8206 of method A.

Transmission path variation estimation unit 8207 of method B receivesreception quadrature baseband signal 7704, and estimates a transmissionpath variation from, e.g., a component of the control channel shown inFIG. 79 of method B, then outputs transmission path variation estimationsignal 8208 of method B.

Information generator 7717 receives the following signals:

-   -   multi-path estimation signal 7706;    -   disturbance intensity estimation signal 7708;    -   received signal strength intensity estimation signal 8202 of        method A signals;    -   received signal strength intensity estimation signal 8204 of        method B signals;    -   transmission path variation estimation signal 8206 of method A;        and    -   transmission path variation estimation signal 8208 of method B,    -   then generator 7717 outputs radio wave propagation environment        estimation signal 7718 corresponding to the information of        received signal strength intensity information symbol 7201,        transmission path variation information symbol 7202, multi-path        information symbol 7203, and disturbance information symbol 7204        shown in FIG. 72.

Received signal strength intensity estimation unit 8209 of method Areceives reception quadrature baseband signal 7729, and estimates areceived signal strength intensity from, e.g., a component of thecontrol channel shown in FIG. 79 of method A of reception quadraturebaseband signal 7729. Estimation unit 8209 then outputs received signalstrength intensity estimation signal 8210 of method A.

Received signal strength intensity estimation unit 8211 of method Breceives reception quadrature baseband signal 7729, and estimates areceived signal strength intensity from, e.g., a component of thecontrol channel shown in FIG. 79 of method B of reception quadraturebaseband signal 7729. Estimation unit 8211 then outputs received signalstrength intensity estimation signal 8212 of method B.

Received signal strength intensity estimation unit 8213 of method Areceives reception quadrature baseband signal 7729, and estimates areceived signal strength intensity from, e.g., a component of thecontrol channel shown in FIG. 79 of method A of reception quadraturebaseband signal 7729. Estimation unit 8213 then outputs received signalstrength intensity estimation signal 8214 of method A.

Received signal strength intensity estimation unit 8215 of method Breceives reception quadrature baseband signal 7729, and estimates areceived signal strength intensity from, e.g., a component of thecontrol channel shown in FIG. 79 of method B of reception quadraturebaseband signal 7729. Estimation unit 8215 then outputs received signalstrength intensity estimation signal 8216 of method B.

Information generator 7742 receives the following signals:

-   -   multi-path estimation signal 7731;    -   disturbance intensity estimation signal 7733;    -   received signal strength intensity estimation signal 8210 of        method A signals;    -   received signal strength intensity estimation signal 8212 of        method B signals;    -   transmission path variation estimation signal 8214 of method A;        and    -   transmission path variation estimation signal 8216 of method B,    -   then generator 7742 outputs radio wave propagation environment        estimation signal 7743 corresponding to the information of        received signal strength intensity information symbol 7201,        transmission path variation information symbol 7202, multi-path        information symbol 7203, and disturbance information symbol 7204        shown in FIG. 72.

The foregoing discussion proves that a switch between the following twotransmission methods improves the information quality:

-   -   a method of transmitting modulation signals of data channels of        a plurality of spread-spectrum communication methods to the same        frequency band from a plurality of antennas; and    -   a method of transmitting a modulation signal of a data channel        of one spread-spectrum communication method to the same        frequency band from one antenna.

Radio-wave propagation environment estimation signals 7718, 7743correspond to signals 7602, 7603 of the transmission apparatus shown inFIG. 76 at the terminal.

Next, an operation at the start of a communication is describedhereinafter. At the start of the communication, if the base stationtransmits modulation signals of data channels of a plurality ofspread-spectrum communication methods to the same frequency band from aplurality of antennas, the terminal does not suit to this transmissionmethod because of, e.g., a bad radio-wave propagation environment. Inthis case, the quality of reception data is lowered.

The transmission signal from the base station is then prepared such thatneither information symbols of method A nor information symbols ofmethod B shown in FIG. 79 are exist. For instance, no plural datachannels are exist at the same frequency band, such as the time ofcontrol symbol 7903 of method A and control symbol 7909 of method B, andthe time of control symbol 7904 of method A and control symbol 7913 ofmethod B as shown in FIG. 79.

Frame structure signal generator 209 shown in FIG. 80 prepares a framestructure at the start of a communication with the terminal such that noplural data channels are exist at the same frequency band, such as thetime of control symbol 7903 of method A and control symbol 7909 ofmethod B, and the time of control symbol 7904 of method A and controlsymbol 7913 of method B as shown in FIG. 79. Generator 209 then outputsthis frame structure as frame structure signal 210.

The reception apparatus shown in FIG. 82 at the terminal estimates aradio-wave propagation environment from the following signals, thenoutputs radio-wave propagation estimation signals 7718, 7743:

-   -   control symbol 7903 of method A and control symbol 7909 of        method B of the transmission signal from the base station shown        in FIG. 80; and    -   control symbol 7904 of method A and control symbol 7913 of        method B of the transmission signal from the base station shown        in FIG. 80.

Transmission apparatus shown in FIG. 76 at the terminal estimates aradio-wave propagation environment from the following signals, thenoutputs radio-wave propagation estimation signals 7718, 7743 withinformation symbols 7913, 7914 shown in FIG. 79:

-   -   control symbol 7903 of method A and control symbol 7909 of        method B of the transmission signal from the base station; and    -   control symbol 7904 of method A and control symbol 7913 of        method B of the transmission signal from the base station.

The reception apparatus shown in FIG. 75 at the base station determinesone of the following transmission methods based on the radio-wavepropagation environment estimation information included in informationsymbol 7913, an element of the transmission signal from the transmissionapparatus shown in FIG. 76 at the terminal:

-   -   a method of transmitting modulation signals of data channels of        a plurality of spread-spectrum communication methods to the same        frequency band from a plurality of antennas; or    -   a method of transmitting a modulation signal of a data channel        of one spread-spectrum communication method to the same        frequency band from one antenna.

Then in the case of a fine environment for radio-wave propagation,modulation signals of data channels of a plurality of spread-spectrumcommunication methods are transmitted to the same frequency band from aplurality of antennas such as information symbols 7901, 7907.

The foregoing discussion proves that the preparation of no data channelsof plural spread-spectrum communication methods existing at the samefrequency band at the start of a communication with the terminal canimprove the quality of information.

In the foregoing description, a modulation signal indicating that theterminal requires a communication with the base station can betransmitted at the beginning

Next, the following method, by which modulation signals of a pluralityof spread-spectrum communication methods can be transmitted, isdescribed with reference to FIGS. 4, 73, 75, 78, 79, 80, 81, and 82:

-   -   a communication method where a modulation signal of the        transmission method, which transmits a control channel, is        transmitted to a receiver, who receives the modulation signal        then estimates radio-wave propagation environment of respective        antennas from reception signals of the control channel, then the        communication method sends the information which requires one of        the following transmission methods based on the estimated        information of the radio-wave propagation environment:    -   a method of transmitting the modulation signals of a plurality        of data channels of the plurality of spread-spectrum        communication methods to the same frequency band from a        plurality of antennas, or    -   a method of transmitting the modulation signal of a data channel        of one spread-spectrum communication method from one antenna;    -   then the communication method selects, based on the requiring        information, one of the foregoing two transmission methods, and    -   a radio communication apparatus using the foregoing        communication method is also described.

FIG. 80 shows the structure of the transmission apparatus at the basestation. Frame structure signal generator 209 receives transmissionmethod determining information 8005, and based on information 8005,outputs the following frame structure information about one of thefollowing two transmission methods as frame structure signal 210:

-   -   a transmission method, where, e.g., information symbol 7901 of        method A and information symbol 7907 of method B shown in FIG.        79 are multiplexed together; or    -   a transmission method, where, information symbol 7902 of method        A is transmitted; however, method B has guard symbol 7908, so        that they are not multiplexed.

Transmission method determining information 8005 corresponds toreception apparatus 7511 shown in FIG. 75 at the base station.

Data-channel modulation and spread unit 8002 receives transmissiondigital signal 8001, frame structure signal 210, then outputstransmission quadrature baseband signal 8003 of method A.

Data-channel modulation and spread unit 8009 receives transmissiondigital signal 8008, frame structure signal 210, then in response toframe structure signal 210, outputs base-band signal 8010 of method B ofthe guard symbol or the information symbol as shown in FIG. 79. At thistime, the modulation signal of the guard symbol corresponds to signalpoint 403 shown in FIG. 4.

Control channel modulation and spread unit 8006 receives transmissionmethod determining information 8005, then outputs transmissionquadrature baseband signal 8007 containing the control information forthe control channel which includes, as shown in FIG. 81, multiplexinformation 8101, pilot symbol 8102, and transmission power controlinformation 8103.

In a similar way to what is discussed above, control channel modulationand spread unit 8012 receives transmission method determininginformation 8005, then outputs transmission quadrature baseband signal8013 containing the control information for the control channel whichincludes, as shown in FIG. 81, multiplex information 8101, pilot symbol8102, and transmission power control information 8103.

Multiplex information 8101 shown in FIG. 81 works as a symbol fornotifying one of the following transmission methods to the terminal:

-   -   a method of multiplexing method A and method B together; or    -   a method of transmitting method A only.

FIG. 75 shows a structure of the reception apparatus of the basestation. Signal isolator 7507 isolates data symbol 7302 fromtransmission method requiring information symbol 7301, then isolator7507 outputs the information of data symbol 7302 as reception data 7509,and outputs also the information of transmission method requiring symbol7301 as transmission requiring information 7508.

Transmission method determining unit 7510 receives transmissionrequiring information 7508, and based on this information, selects oneof the following transmission methods:

-   -   a method of transmitting modulation signals of data channels of        a plurality of spread-spectrum communication methods to the same        frequency band from a plurality of antennas; or    -   a method of transmitting a modulation signal of a data channel        of one spread-spectrum communication method to the same        frequency band from one antenna.

Determining unit 7510 then outputs the information about thetransmission method as transmission method determining information 7511and multiplex information 7512.

FIG. 78 shows the structure of the transmission apparatus at theterminal. Transmission method requiring information generator 7801receives radio-wave propagation environment estimation signals 7602,7603, then outputs transmission method requiring information 7802.Modulation signal generator 7606 receives transmission digital signal7601, transmission requiring information 7802, and frame structuresignal 7605, and outputs modulation signal 7607 according to the framestructure shown in FIG. 73. Radio-wave propagation environmentestimation signals 7602, 7603 correspond to estimation signals 7718,7743 of the reception apparatus shown in FIG. 82 at the terminal.

FIG. 82 shows the structure of the reception apparatus at the terminal.Received signal strength intensity estimation unit 8201 ofspread-spectrum communication method A receives reception quadraturebaseband signal 7704, and estimates a received signal strength intensityfrom, e.g., a component of the control channel shown in FIG. 79 ofmethod A of reception quadrature baseband signal 7704. Estimation unit8201 then outputs received signal strength intensity estimation signal8202 of method A.

Received signal strength intensity estimation unit 8203 ofspread-spectrum communication method B receives reception quadraturebaseband signal 7704, and estimates a received signal strength intensityfrom, e.g., a component of the control channel shown in FIG. 79 ofmethod B of reception quadrature baseband signal 7704. Estimation unit8203 then outputs received signal strength intensity estimation signal8204 of method B.

Transmission path variation estimation unit 8205 of method A receivesreception quadrature baseband signal 7704, and estimates a transmissionpath variation from, e.g., a component of the control channel of methodA shown in FIG. 79, then outputs transmission path variation estimationsignal 8206 of method A.

Transmission path variation estimation unit 8207 of method B receivesreception quadrature baseband signal 7704, and estimates a transmissionpath variation from, e.g., a component of the control channel of methodB shown in FIG. 79, then outputs transmission path variation estimationsignal 8208 of method B.

Information generator 7717 receives the following signals:

-   -   multi-path estimation signal 7706;    -   disturbance intensity estimation signal 7708;    -   received signal strength intensity estimation signal 8202 of        method A signals;    -   received signal strength intensity estimation signal 8204 of        method B signals;    -   transmission path variation estimation signal 8206 of method A;        and    -   transmission path variation estimation signal 8208 of method B,    -   then generator 7717 outputs radio wave propagation environment        estimation signal 7718 corresponding to the information of        received signal strength intensity information symbol 7201,        transmission path variation information symbol 7202, multi-path        information symbol 7203, and disturbance information symbol 7204        shown in FIG. 72.

Received signal strength intensity estimation unit 8209 of method Areceives reception quadrature baseband signal 7729, and estimates areceived signal strength intensity from, e.g., a component of thecontrol channel shown in FIG. 79 of method A of reception quadraturebaseband signal 7729. Estimation unit 8209 then outputs received signalstrength intensity estimation signal 8210 of method A.

Received signal strength intensity estimation unit 8211 of method Breceives reception quadrature baseband signal 7729, and estimates areceived signal strength intensity from, e.g., a component of thecontrol channel shown in FIG. 79 of method B of reception quadraturebaseband signal 7729. Estimation unit 8211 then outputs received signalstrength intensity estimation signal 8212 of method B.

Received signal strength intensity estimation unit 8213 of method Areceives reception quadrature baseband signal 7729, and estimates areceived signal strength intensity from, e.g., a component of thecontrol channel shown in FIG. 79 of method A of reception quadraturebaseband signal 7729. Estimation unit 8213 then outputs received signalstrength intensity estimation signal 8214 of method A.

Received signal strength intensity estimation unit 8215 of method Breceives reception quadrature baseband signal 7729, and estimates areceived signal strength intensity from, e.g., a component of thecontrol channel shown in FIG. 79 of method B of reception quadraturebaseband signal 7729. Estimation unit 8215 then outputs received signalstrength intensity estimation signal 8216 of method B.

Information generator 7742 receives the following signals:

-   -   multi-path estimation signal 7731;    -   disturbance intensity estimation signal 7733;    -   received signal strength intensity estimation signal 8210 of        method A signals;    -   received signal strength intensity estimation signal 8212 of        method B signals;    -   transmission path variation estimation signal 8214 of method A;        and    -   transmission path variation estimation signal 8216 of method B,    -   then generator 7742 outputs radio wave propagation environment        estimation signal 7743 corresponding to the information of        received signal strength intensity information symbol 7201,        transmission path variation information symbol 7202, multi-path        information symbol 7203, and disturbance information symbol 7204        shown in FIG. 72.

The foregoing discussion proves that a switch between the following twotransmission methods improves the information quality:

-   -   a method of transmitting modulation signals of data channels of        a plurality of spread-spectrum communication methods to the same        frequency band from a plurality of antennas; and    -   a method of transmitting a modulation signal of a data channel        of one spread-spectrum communication method to the same        frequency band from one antenna.

Radio-wave propagation environment estimation signals 7718, 7743correspond to signals 7602, 7603 of the transmission apparatus shown inFIG. 76 at the terminal.

Next, an operation at the start of a communication is describedhereinafter. At the start of the communication, if the base stationtransmits modulation signals of data channels of a plurality ofspread-spectrum communication methods to the same frequency band from aplurality of antennas, the terminal does not suit to this transmissionmethod because of, e.g., a bad radio-wave propagation environment. Inthis case, the quality of reception data is lowered.

The transmission signal from the base station is then prepared such thatneither information symbols of method A nor information symbols ofmethod B shown in FIG. 79 are exist. For instance, no plural datachannels are exist at the same frequency band, such as the time ofcontrol symbol 7903 of method A and control symbol 7909 of method B, andthe time of control symbol 7904 of method A and control symbol 7913 ofmethod B as shown in FIG. 79.

Frame structure signal generator 209 shown in FIG. 80 prepares a framestructure at the start of a communication with the terminal such that noplural data channels are exist at the same frequency band, such as thetime of control symbol 7903 of method A and control symbol 7909 ofmethod B, and the time of control symbol 7904 of method A and controlsymbol 7913 of method B as shown in FIG. 79. Generator 209 then outputsthis frame structure as frame structure signal 210.

The reception apparatus shown in FIG. 82 at the terminal estimates aradio-wave propagation environment from the following signals, thenoutputs radio-wave propagation estimation signals 7718, 7743:

-   -   control symbol 7903 of method A and control symbol 7909 of        method B of the transmission signal from the base station shown        in FIG. 80; and    -   control symbol 7904 of method A and control symbol 7913 of        method B of the transmission signal from the base station shown        in FIG. 80.

Transmission method requiring information generator 7801 of thetransmission apparatus shown in FIG. 78, based on radio-wave propagationenvironment estimation signals 7718 and 7743 discussed above, transmitsinformation which requires one of the following transmission method asthe transmission requiring information with information symbols 7913,7914 shown in FIG. 79:

-   -   a method of transmitting modulation signals of data channels of        a plurality of spread-spectrum communication methods to the same        frequency band from a plurality of antennas; or    -   a method of transmitting a modulation signal of a data channel        of one spread-spectrum communication method to the same        frequency band from one antenna.

The reception apparatus shown in FIG. 75 at the base station determinesone of the following transmission methods based on the radio-wavepropagation environment estimation information included in informationsymbol 7913, which is an element of the transmission signal from thetransmission apparatus shown in FIG. 76 at the terminal:

-   -   a method of transmitting modulation signals of data channels of        a plurality of spread-spectrum communication methods to the same        frequency band from a plurality of antennas; or    -   a method of transmitting a modulation signal of a data channel        of one spread-spectrum communication method to the same        frequency band from one antenna.

Then the modulation signals of the transmission method determined aretransmitted from the antenna.

The foregoing discussion proves that the preparation of no data channelsof plural spread-spectrum communication methods existing at the samefrequency band at the start of a communication with the terminal canimprove the quality of information.

In the foregoing description, a modulation signal indicating that theterminal requires a communication with the base station can betransmitted at the beginning

In the foregoing description, as shown in FIG. 79, the control channelexists in both of spread-spectrum communication methods A and B;however, e.g., this embodiment is applicable to the case where thecontrol channel exits only in method A, as shown in FIG. 83. In thiscase, the transmission apparatus in FIG. 80 does not have controlchannel modulation and spread unit 8012 of method B.

This embodiment refers to the case where the number of spread-spectrumcommunication methods to be multiplexed are switched between twochannels and one channel; however, this example does not limit theembodiment. For instance, in the case where three methods can bemultiplexed to the same frequency band, the transmission apparatus atthe base station switches the number of multiplexing between 1-3methods.

This embodiment is also applicable to the case where signals of aspread-spectrum communication method is modulated by OFDM method. Astructure of a control symbol of a spread-spectrum communication methodtransmitted from the base station in this case is shown in FIGS. 85 and86. In FIG. 85, the control symbols are spread on the time axis, whilethey are spread on the frequency axis in FIG. 86. Information symbolsare also spread either on a time axis or a frequency axis as shown inFIGS. 85 and 86, so that they are multiplexed to signals of the controlchannels. The transmission apparatus and the reception apparatus both atthe base station and the terminal can be formed of elements described inFIGS. 75, 76, 78, 80 and 82 which are referred to the frame structureshown in FIG. 70.

In this embodiment, one data channel per method A or method B is usedfor the description purpose; however, the number of data channels is notlimited to one, and plural data channels are applicable to thisembodiment. Codes to be used for spread or inverse-spread ofspread-spectrum communication methods A and B can be identical to eachother or different from each other.

The expression of “antenna” in the previous description does not alwaysmean a single antenna, but “antenna” can mean an antenna unit which isformed of a plurality of antennas.

The previous discussion refers to the following method, by whichmodulation signals of a plurality of spread-spectrum communicationmethods can be transmitted:

-   -   the communication method where a modulation signal of a        transmission method, which transmits a control channel, is        transmitted to a receiver, who receives the modulation signal        then estimates radio-wave propagation environment of respective        antennas from reception signals of the control channel, and        transmits the estimated information of the radio-wave        propagation environment, then the communication method selects        one of the following transmission methods based on the estimated        information:    -   a method of transmitting the modulation signals of a plurality        of data channels of the plurality of spread-spectrum        communication methods to the same frequency band from a        plurality of antennas, or    -   a method of transmitting the modulation signal of one data        channel of one spread-spectrum communication method from one        antenna.

The previous discussion also refers to the radio communication apparatususing the foregoing communication method.

The discussion above also describes the method below, by whichmodulation signals of a plurality of spread-spectrum communicationmethods can be transmitted:

-   -   the communication method where a modulation signal of the        transmission method, which transmits a control channel, is        transmitted to a receiver, who receives the modulation signal        then estimates radio-wave propagation environment of respective        antennas from reception signals of the control channel, then the        communication method sends the information which requires one of        the transmission methods below based on the information of the        estimated radio-wave propagation environment:    -   a method of transmitting the modulation signals of a plurality        of data channels of the plurality of spread-spectrum        communication methods to the same frequency band from a        plurality of antennas, or    -   a method of transmitting the modulation signal of a data channel        of one spread-spectrum communication method from one antenna;    -   then the communication method selects, based on the requiring        information, one of the foregoing two transmission methods.

The discussion above also refers to the radio communication apparatususing the communication method. In conclusion, the methods and theapparatuses discussed above allow transmitting information moreaccurately.

INDUSTRIAL APPLICABILITY

The present invention is useful for a transmission and reception methodby which modulation signals of a plurality of channels are multiplexedto the same frequency band. The present invention allows estimatingchannels accurately and with ease for demultiplexing multiplexedmodulation signals received by a reception apparatus.

While illustrative embodiments have been illustrated and described, itwill be appreciated that various changes can be made therein withoutdeparting from the spirit and scope of the invention.

The invention claimed is:
 1. A method of generating modulation signals,the method comprising: generating a plurality of modulation signals eachof which is to be transmitted from a different one of a plurality ofantennas in an identical frequency band, wherein each modulation signalincludes a pilot symbol sequence comprising a plurality of pilot symbolsused for demodulation; inserting each of the pilot symbol sequences atthe same temporal point in each modulation signal, wherein the pilotsymbol sequences are orthogonal to each other with zero mutualcorrelation among the plurality of modulation signals, each pilot symbolhaving a non-zero amplitude, a quantity of the plurality of pilotsymbols in each sequence being greater than a quantity of the pluralityof modulation signals to be transmitted; and outputting the plurality ofmodulation signals, each comprising different transmission data and oneof the pilot symbol sequences, to the plurality of antennas.
 2. Themethod of claim 1, wherein the plurality of pilot symbols used fordemodulation are symbols used for estimating a frequency offset.
 3. Themethod of claim 1, wherein the plurality of pilot symbols used fordemodulation each comprise a complex number.
 4. The method of claim 1,wherein each of the plurality of modulation signals comprises a frame asa unit and the frame includes the pilot symbol sequence used fordemodulation.
 5. The method of claim 1, wherein the plurality ofmodulation signals are transmitted by a transmitting apparatus and thetransmitting apparatus comprises the plurality of antennas.
 6. Themethod of claim 1, wherein the plurality of modulation signals comprisedata symbols.
 7. The method of claim 1, wherein the plurality of pilotsymbols used for demodulation are symbols used to estimate atransmission path fluctuation.
 8. The method of claim 1, wherein theplurality of pilot symbols used for demodulation comprise phase shiftkeying (PSK) modulation symbols.
 9. A signal generation apparatusconfigured to generate modulation signals, the apparatus comprising oneor more processing devices configured to: generate a plurality ofmodulation signals each of which is to be transmitted from a differentone of a plurality of antennas in an identical frequency band, whereineach modulation signal includes a pilot symbol sequence each comprisinga plurality of pilot symbols used for demodulation; insert each of thepilot symbol sequences at the same temporal point in each modulationsignal; and output the plurality of modulation signals, each comprisingdifferent transmission data and one of the pilot symbol sequences, tothe plurality of antennas, wherein the pilot symbol sequences areorthogonal to each other with zero mutual correlation among theplurality of modulation signals, each pilot symbol having a non-zeroamplitude, a quantity of the plurality of pilot symbols in each sequencebeing greater than a quantity of the plurality of modulation signals tobe transmitted.